One in prison for fraud? (3)

I believe the answer is:

con

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'for fraud?' is the definition.
(con is a kind of fraud)

I can't explain the remainder of the clue.

(Other definitions for con that I've seen before include "Rook" , "Learn; swindle" , "Prisoner (sl.)" , "Direct steering; study" , "do something?" .)

I've seen this clue in the Evening Standard.

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