Forgive a bishop on crack (7)
I believe the answer is:
absolve
'forgive' is the definition.
(absolving is a kind of forgiving)
'a bishop on crack' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'on' says to put letters next to each other.
'crack' becomes 'solve' (I've seen this before).
'a'+'b'+'solve'='ABSOLVE'
(Other definitions for absolve that I've seen before include "Discharge" , "Let off the hook" , "free of error" , "Clear of blame or guilt" , "Give pardon" .)