Competition buzzer (3)
I believe the answer is:
bee
I believe this is a double definition.
'competition' is the first definition.
(I've seen this before)
'buzzer' is the second definition.
(insect which buzzes)
(Other definitions for bee that I've seen before include "Stinging insect" , "Honey producer" , "In one's bonnet, it's an obsessive idea" , "Busy person" , "Flying insect (often busy)" .)