Wicked bit of singing (3)

I believe the answer is:

sin

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But I can't explain it at all! Could you help me understand?

(Other definitions for sin that I've seen before include "Immoral act" , "Lapse against moral law" , "Wrongdoing" , "Wicked deed" , "Breach of moral code" .)

I've seen this clue in the Evening Standard.

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