Disconcert, but only for an instant (5)

I believe the answer is:

shake

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This clue could be a double definition.

'disconcert but only for' is the first definition.
'shake' can be an answer for 'disconcert' (thesaurus). I'm not certain of the 'but only for' bit.

'an instant' is the second definition.
(thesaurus)

Can you help me to learn more?

(Other definitions for shake that I've seen before include "Frothy milk drink" , "Rattle" , "wave" , "moment" , "Flavoured milk drink" .)

I've seen this clue in the Evening Standard.

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