Put nuts back, having no time when night's over (3,2)

I believe the answer is:

sun up

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'when night's over' is the definition.
(sunrise)

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

(Other definitions for sun up that I've seen before include "Twenty two [FIRST LIGHT] American" , "first thing?" .)

I've seen this clue in The Guardian.

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