One briefly imprisoned for a trick?

I believe the answer is:

con

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'for a trick?' is the definition.
(a con is a fraud or trick)

I can't explain the rest of the clue.

(Other definitions for con that I've seen before include "Direct steering; study" , "Scam, swindle" , "Informally swindle" , "one in pen?" , "Swindle after winning trust" .)

I've seen this clue in the Evening Standard.

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