Stomach empty, by the sound of it (4)
I believe the answer is:
bear
'stomach' is the definition.
(both can mean to tolerate or endure)
'empty by the sound of it' is the wordplay.
'empty' becomes 'bare' (similar in meaning).
'by the sound of it' indicates a 'sounds like' (homophone) clue.
'bare' sounds like 'BEAR'.
(Other definitions for bear that I've seen before include "Carry; large mammal" , "live with" , "stomach and > suffer" , "Large, shaggy-coated mammal" , "Carry or endure" .)