A crime? Yes, when there's no love lost! (3)

I believe the answer is:

sin

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'a crime?' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

(Other definitions for sin that I've seen before include "Lapse against moral law" , "Moral offence" , "Breach of morality" , "Something wrong" , "Wrongdoing" .)

I've seen this clue in the Evening Standard.

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