Drone with loose filament (5)
I believe the answer is:
thrum
'drone' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for thrum that I've seen before include "Repetitive sound" , "Fringe, tassel of unwoven threads" , "Play monotonously" , "Make a continuous humming sound" , "Strum, hum or drum!" .)