Grant forgiveness (6)
I believe the answer is:
pardon
'grant forgiveness' is the definition.
(pardoning is a kind of granting forgiveness)
This is all the clue.
(Other definitions for pardon that I've seen before include "Excuse or absolve" , "Forgive or remit" , "Excuse me, kindly overlook" , "Ask this to seek forgiveness" , "Forgive the polite interruption" .)