Be heard as a buzzer (3)
I believe the answer is:
bee
'a buzzer' is the definition.
(insect which buzzes)
'be heard' is the wordplay.
'heard' shows a homophone (sound like).
'be' sounds like 'BEE'.
'as' acts as a link.
(Other definitions for bee that I've seen before include "Insect, may be in bonnet" , "Hymenopterous insect" , "Busy person" , "Creator of honey" , "Honey maker" .)