Stun people who are inside entertaining clubs with cruciverbalists (7)

I believe the answer is:

concuss

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'stun' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for concuss that I've seen before include "Stun with heavy blow" , "Knock it on the head!" , "Cause a brain injury" , "Completely stun" , "Inflict (temporary) damage on the brain" .)

I've seen this clue in The Times.

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