Lack of restraint with an orchestra playing?
I believe the answer is:
abandon
'lack of restraint' is the definition.
(I've seen this in another clue)
'with an orchestra playing?' is the wordplay.
'with' means one lot of letters go next to another.
'an' becomes 'a'.
'orchestra' becomes 'band' (I've seen this before).
'playing?' becomes 'on'.
'a' next to 'band' is 'aband'.
'aband'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Forsake with recklessness" , "Desert; intemperance" , "Forsake - careless freedom" , "Walk out on" , "Leave in the lurch" .)