Cool headed flier involved in crime (5)
I believe the answer is:
crook
'involved in crime' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'cool headed flier' is the wordplay.
I cannot really see how this works, but
'flier' could be 'rook' (rook is a kind of birdanimal) and 'rook' is found in the answer.
A single letter 'c' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for crook that I've seen before include "Something kinky" , "Shepherd's staff" , "Hooked staff" , "Bend; criminal; staff" , "Swindler - crosier - ill (in Australia)" .)