Sleeping sound (5)
I believe the answer is:
snore
'sleeping sound' 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 "How to keep someone awake while sleeping?" , "Sound made by sleeper" , "Grunting sound" , "Make raucous nocturnal noise" , "Noise from a sleeper" .)