Quick look from both sides (4)

I believe the answer is:

peep

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'quick look' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for peep that I've seen before include "Look furtively (in both directions)" , "Furtive look" , "Look surreptitiously - through a keyhole?" , "Look surreptitiously, like Tom" , "Peek" .)

I've seen this clue in The Daily Express.

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