See a flier as a criminal (5)
I believe the answer is:
crook
'a criminal' is the definition.
(synonyms)
'see a flier' is the wordplay.
'see' becomes 'c' (the word for the letter, according to Chambers).
'a flier' becomes 'rook' (rook is a kind of birdanimal).
'c'+'rook'='CROOK'
'as' acts as a link.
(Other definitions for crook that I've seen before include "Professional criminal" , "Shepherd's staff" , "Criminal - taken in hand by bishop" , "Swindler - crosier - ill (in Australia)" , "Fence, perhaps" .)