A bishop with touching lack of restraint (7)
I believe the answer is:
abandon
'lack of restraint' is the definition.
(I've seen this before)
'a bishop with touching' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'with' becomes 'and' (I've seen this before**).
'touching' becomes 'on'.
'a'+'b'+'and'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Forsake with recklessness" , "Completely give up; desert" , "Kick" , "Give up; leave behind" , "Walk out on" .)