Spy that could go either way (4)

I believe the answer is:

peep

I believe this is a double definition.

'spy' is the first definition.
(thesaurus)

'that could go either way' is the second definition.

(Other definitions for peep that I've seen before include "Sly look (palindrome)" , "Furtive look" , "Chirp" , "Large underground chamber" , "Look quickly" .)

I've seen this clue in The Telegraph.

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