More importantly, while American solvers are challenged to deduce an answer from a relatively straight forward clue, the UK puzzler must first unscramble the clue. For it is the clue itself which has been encrypted and therein lies the challenge. To ensure a level playing field between the setter (the clue writer in Brit jargon) and the solver, there are established guidelines for the various devices the setter can employ when setting the clues. After all, there is no play value in a puzzle with clues encrypted beyond a person's ability to solve it.
The underlying rule for all cryptic clues, with a few exceptions, is that they consist of two parts: a straight definition and some form of wordplay that will bring the solver to the correct answer. The solver must first establish where the straight part ends and the cryptic part begins (or vice versa). As mentioned, there are, fortunately, some "fair practice' guidelines which affords the solver a toe-hold to begin his or her task of solving the clue.
There is a certain array of devices that the setter can use when writing the clues and each device, with a couple of exceptions, has certain words associated with it that indicate to the solver which device the setter has used. However, these indicator words do not comprise a hard and fast vocabulary but allow the setter a certain amount of leeway. The more clever or nuanced the choice of words the more entertaining the clue and the more satisfying the solver's sense of accomplishment when he or she succeeds. Here are the main devices used when setting cryptic clues.
The letters of the answer have been rearranged to form another word.
The indicator word will suggest mixing, scrambling, reordering, etc.
Example clue: Transplant me a lilac for a flowery shrub (8)
Straight definition: 'a flowery shrub'
Cryptic definition: 'Transplant me a lilac'
The indicator word is 'transplant' and the anagram fodder is 'me a lilac' which becomes CAMELLIA = 'a flowery shrub'
The answer word is hidden within the clue.
The indicator word will suggest, to observe, is appearing, being seen, showing, etc.
Example clue: Look at ease as he'll get scallops home (8)
Straight definition: 'scallops home'
Cryptic definition: 'Look at ease as he'll'
The indicator word(s) is 'look at' and the container is 'ease as he'll' where the hidden word is 'SEASHELL' = 'scallops home'
Two different definitions which combine in a misleading way but actually lead to the same answer. These clues are usually short and sweet.
Example clue: Boom box (4)
First definition: 'boom' = SPAR (as on a sailboat)
Second definition: 'box' = SPAR (in a boxing ring)
Part of the misdirection is the clue brings to mind a 'boombox' or portable tape player.
Just as in a game of charades, the answer word or phrase is broken down into fragments and each component is clued separately. Even single letters can be clued. For example, E, W, N & S can be clued as compass points; V=5; L=50,D=500 (Roman numerals).
More playful clues could include 'cottontail' for N, 'bulkhead' for B, 'center of the earth' for R; 'empty pocket' for PT.
Example clue: Out of bounds, it's trendy to go AWOL (4,4)
Straight definition: 'go AWOL'
Cryptic definition: 'Out of bounds, it's trendy'
'bounds = jumps; it's trendy = hip; out of 'jumps' and 'hip' one can make 'JUMP SHIP' (go AWOL)
Certain words contain other words within them and they are clued separately. For example, the word APPEARED contains the word PEAR inside the word APED.
The indicator word will suggest within, having, holding, embracing, gripping, etc.
Example clue: Looking feverish, the sot is inside well-nourished (7)
Straight definition: 'looking feverish'
Cryptic definition: 'the sot is inside well-nourished'
'the sot' (LUSH) is inside 'well-nourished' (FED), hence F(LUSH)ED = 'looking feverish'
The answer runs back within the clue (or from bottom to top in a down clue).
The indicator word will suggest going back, returning, a replay, rerun, etc. (or rising, going up, ascending, etc., in a down clue).
Example clue: Director Benedek appears in Warhol's, "A Look Back" (5)
Straight definition: 'Director Benedek'
Cryptic definition: 'appears in Warhol's, "A Look Back"'
Looking back in 'Warhol's, "A Look' is the name 'laslo; Director Benedek = LASLO
The solver must remove certain elements as directed in the clue to arrive at the answer.
The indicator word will suggest cutting, lopping, trimming, erasing, losing, etc.
Example clue (for a vertical entry): Topless lady looks like our first gardener (4)
Straight definition: 'our first gardener'
Cryptic definition: 'topless lady'
'topless lady' = MADAM - M = ADAM = 'our first gardener'
A word that sounds like another word is substituted for the answer.
The indicator word will suggest hearing, reported, stated, announced, etc.
Example clue: Not many heard the survivor's first word (4)
Straight definition: 'not many'
Cryptic definition: 'the survivor's first word'
'not many' (heard) = FEW which sounds like PHEW = 'the survivor's first word'
&lit! (And literally)
This is probably the hardest clue to set and perhaps the most rewarding to solve. It generally provides a very intense 'Aha!' moment when the answer finally dawns on the solver. This type of clue is identified with an exclamation mark at the end. It indicates that the clue can be read twice in its entirety to reach two different definitions which in turn clue a single answer.
Example clue: Revolver! (6,5)
First definition: Beatles album
Second definition: it goes around (revolves) on a turntable
Solution: RECORD ALBUM
These are the basic types of cryptic clues one will encounter. However, keep in mind that some clues may employ a combination of these techniques. Also, different setters will use different indicator words and the more accomplished ones are very devious and devilishly clever in their ability to misdirect. That is the goal of the setter: to send you off in the wrong direction.
Above all, bear in mind the words of AF Ritchie, who laid down what became the first commandment of cryptic crosswords: "I need not mean what I say, but I must say what I mean." To be a legitimate cryptic clue, there should be fair wordplay and no extraneous fill.