Look at edgy playmate going to and fro (4)

I believe the answer is:

peep

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'look' is the definition.
(peep can mean to look at something)

I don't understand how the rest of the clue works.

(Other definitions for peep that I've seen before include "Look furtively or voyeuristically" , "Take quick look" , "Sly look (palindrome)" , "Large underground chamber" , "Secret look" .)

I've seen this clue in The Irish Times.

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