Lion's bellow (4)
I believe the answer is:
roar
'lion's bellow' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roar that I've seen before include "Lion's call" , "Loud noise of angry bull" , "Lion's noise" , "Make loud angry sound like lion" , "24 [BOOM]" .)