Forgive a bishop's crack (7)
I believe the answer is:
absolve
'forgive' is the definition.
(absolving is a kind of forgiving)
'a bishop's crack' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'crack' becomes 'solve' (I've seen this before).
'a'+'b'+'solve'='ABSOLVE'
(Other definitions for absolve that I've seen before include "Forgive sins" , "Lob vase (anag.)" , "Discharge" , "Declare (someone) free of guilt" , "Grant remission of sins" .)