Sleep soundly? (5)
I believe the answer is:
snore
'sleep soundly?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for snore that I've seen before include "Make raucous nasal sound during sleep" , "Make racous nocturnal sound" , "Make noises sleeping" , "Make raucous nocturnal noise" , "Noise indicating sleep" .)