Go off when you overindulge (5)

I believe the answer is:

spoil

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'go off' is the definition.
(thesaurus)

I can't explain the remainder of the clue.

(Other definitions for spoil that I've seen before include "Having dredged-up material" , "Mess up" , "Butcher" , "Harm or destroy" , "decompose" .)

I've seen this clue in the Evening Standard.

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