Play a mandolin (5)
I believe the answer is:
strum
'play a mandolin' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for strum that I've seen before include "Play with sweeps of fingers" , "Sweepingly sound guitar strings" , "Sweep fingers over strings" , "Play a stringed instrument (badly)" , "Play badly on a guitar" .)