Yes, a bit of fun's wrong! (3)

I believe the answer is:

sin

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'wrong' is the definition.
(wrong can mean a sin or crime)

I can't explain the remainder of the clue.

(Other definitions for sin that I've seen before include "Serious error" , "Immoral act" , "Immoral action" , "Evil" , "Err" .)

I've seen this clue in the Evening Standard.

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