Leave a group of musicians playing (7)
I believe the answer is:
abandon
'leave' is the definition.
(abandoning is a kind of leaving)
'a group of musicians playing' is the wordplay.
'group of musicians' becomes 'band' (I've seen this before).
'playing' becomes 'on'.
'a'+'band'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Desert; intemperance" , "Give up; leave behind" , "dump" , "Lack of inhibition; desert" , "Jack in" .)