Lack of restraint shown by a group performing (7)
I believe the answer is:
abandon
'lack of restraint' is the definition.
(I've seen this before)
'shown by a group performing' is the wordplay.
'shown by' is a charade indicator (letters next to each other).
'group' becomes 'band' (band is a kind of group).
'performing' becomes 'on' (I've seen this in other clues).
'a' put next to 'band' is 'aband'.
'aband'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Desert, strand" , "dump" , "Leave in the lurch" , "Completely give up; desert" , "Czech city" .)