Rest of the night (5)

I believe the answer is:

sleep

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'rest' is the definition.
(I know that rest can be written as sleep)

I don't understand the rest of the clue.

(Other definitions for sleep that I've seen before include "Be dormant" , "Slumber" , "crash" , "Snooze" , "Natural state of unconscious rest" .)

I've seen this clue in The Globe and Mail.

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