Leave an orchestra performing (7)
I believe the answer is:
abandon
'leave' is the definition.
(to abandon is to leave or desert)
'an orchestra performing' is the wordplay.
'an' becomes 'a'.
'orchestra' becomes 'band' (large musical group).
'performing' becomes 'on' (as in being on stage).
'a'+'band'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Forsake with recklessness" , "Desert - it's wild" , "Leave, desert" , "Desert; give up (action)" , "Completely give up; desert" .)