Usually, the rest of the night (5)
I believe the answer is:
sleep
'rest of the night' is the definition.
'sleep' can be an answer for 'rest' (synonyms). I am not certain of the 'of the night' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sleep that I've seen before include "Doze, nap" , "Be dormant" , "crash" , "Produced (egg)" , "Wayne _; former Royal Ballet principal dancer" .)