Sleeper's sound (5)
I believe the answer is:
snore
'sleeper's sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for snore that I've seen before include "Sound made by sleeper" , "6 made by sleeper" , "Grunting sound" , "Breathe noisily during sleep" , "Make raucous nasal sound during sleep" .)