One opening in seventeen (4)

I believe the answer is:

vent

'one opening' is the definition.
(vent is a kind of opening)

'in seventeen' is the wordplay.
'in' says the answer is hidden in the clue.
'VENT' is hidden in the letters of 'seventeen'.

(Other definitions for vent that I've seen before include "[BLOWHOLE] ?" , "Volcanic opening" , "Give outlet as to feelings" , "Opening for air" , "Opening releasing gas" .)

I've seen this clue in the Evening Standard.

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