The buzzer was quiet (4)
I believe the answer is:
wasp
'the buzzer' is the definition.
(I've seen this before)
'was quiet' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'was'+'p'='WASP'
(Other definitions for wasp that I've seen before include "Buzzer" , "Striped stinger" , "Being in the American elite" , "Influential American" , "type dominant across the pond" .)