Don't let it happen prior to opening (7)

I believe the answer is:

prevent

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'don't let it happen' is the definition.
I can't tell whether this defines the answer.

'prior to opening' is the wordplay.
'prior to' becomes 'pre' (I've seen this in another clue).
'opening' becomes 'vent' (a vent is an opening or outlet).
'pre'+'vent'='PREVENT'

Can you help me to learn more?

(Other definitions for prevent that I've seen before include "Stop, hinder" , "Keep from arising" , "Keep from happening" , "Stop from happening" , "Thwart" .)

I've seen this clue in The Irish Times.

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