Jug-band instrument (5)
I believe the answer is:
kazoo
'jug-band instrument' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for kazoo that I've seen before include "Simple musical instrument" , "Toy-like instrument into which one hums" , "Humming toy" , "Toy wind instrument that buzzes" .)