Slumbers (6)
I believe the answer is:
sleeps
'slumbers' is the definition.
('sleep' can be a synonym of 'slumber')
This is all the clue.
(Other definitions for sleeps that I've seen before include "Takes a siesta" , "Rests in the arms of Morpheus" , "Dozes" , "Slumbers" , "Catches some Z's" .)