One in prison for a trick? (3)
I believe the answer is:
con
'for a trick?' is the definition.
(a con is a fraud or trick)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for con that I've seen before include "Tory" , "Direct steering; study" , "Swindle or see" , "Fleece" , "Rook" .)