Twitchy finger's back on the buzzer (6)
I believe the answer is:
hornet
'buzzer' is the definition.
(something that buzzes)
'twitchy finger's back on the' is the wordplay.
'twitchy' indicates an anagram (I've seen this in other clues).
'back' says to take the final letters.
The final letter of 'finger' is 'r'.
'r'+'on'+'the'='ronthe'
'ronthe' with letters rearranged gives 'HORNET'.
(Other definitions for hornet that I've seen before include "Small flier" , "Large stinging wasp" , "Large wasp with vicious sting" , "Throne for a kind of wasp" , "Vespa" .)