Band leader (3)
I believe the answer is:
bee
'band leader' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bee that I've seen before include "Useful insect" , "Hive worker" , "Hive insect" , "In one's bonnet, it's an obsessive idea" , "Apian insect" .)