Bellows (5)
I believe the answer is:
roars
'bellows' is the definition.
('roar' can be a synonym of 'bellow')
This is all the clue.
(Other definitions for roars that I've seen before include "Calls like lion" , "Sounds like a lion" , "Bellows like a bull" , "'Deep, bellowing bursts of sound (5)'" , "Deep bellows" .)