Time flies? It might! (4)
I believe the answer is:
bird
'time' is the definition.
(both are slang for a prison sentence)
I cannot understand how the remainder of the clue works.
(Other definitions for bird that I've seen before include "Creature - time in prison" , "chat, perhaps?" , "Dawn chorus etc - book by Sebastian Faulks" , "Flier - spell in prison" , "Flying creature" .)