Unrested, somehow, set to come out at night (8)
I believe the answer is:
dentures
'set to come out at night' is the definition.
'unrested somehow' is the wordplay.
'somehow' indicates an anagram.
'unrested' is an anagram of 'DENTURES'.
(Other definitions for dentures that I've seen before include "Set of false teeth" , "Underset in teeth" , "Sets of artificial teeth." .)