Briefly check for shock (4)

I believe the answer is:

stun

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'for shock' is the definition.
('stun' can be a synonym of 'shock')

I cannot understand how the rest of the clue works.

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(Other definitions for stun that I've seen before include "cause amazement" , "Daze, overwhelm" , "Daze, render semi-conscious" , "Shock or astonish" , "Make senseless or dizzy with a blow" .)

I've seen this clue in The Independent.

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