Open at lunch break (7)

I believe the answer is:

unlatch

'open' is the definition.
(thesaurus)

'at lunch break' is the wordplay.
'break' is an anagram indicator.
'at'+'lunch'='atlunch'
'atlunch' with letters rearranged gives 'UNLATCH'.

(Other definitions for unlatch that I've seen before include "Unfasten (a door)" , "Free bar" .)

I've seen this clue in The Globe and Mail and The Guardian.

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