Sinner's punishment (7)
I believe the answer is:
penance
'sinner's punishment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for penance that I've seen before include "humiliating act" , "Mortification" , "Punishment for wrongdoing, by religion perhaps" , "Act of atonement" , "Punishment inflicted on oneself" .)