Slumbered (5)
'slumbered' is the definition.
('sleep' can be a synonym of 'slumber')
This is the entire clue.
(Other definitions for slept that I've seen before include "Napped, dozed" , "Had room for" , "Was dormant" , "Snoozed" , "appeared still" .)
(Another definition for dozed that I've seen is " Slept lightly".)