Baker's dozens enter this sack (9)

I believe the answer is:

thirteens

'baker's dozens' is the definition.
('thirteen' can be a synonym of 'baker's dozen')

'enter this sack' is the wordplay.
'sack' indicates an anagram (sack can mean destroy or spoil).
'enter'+'this'='enterthis'
'enterthis' is an anagram of 'THIRTEENS'.

(Another definition for thirteens that I've seen is " numbers".)

I've seen this clue in The Guardian.

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