What to forgive? (6)
I believe the answer is:
pardon
I believe this clue is a double definition.
'what' is the first definition.
(I've seen this before)
'forgive?' is the second definition.
(I know that pardon is a more specific form of forgive)
'to' is the link.
(Other definitions for pardon that I've seen before include "Forgive - eh?" , "Ask this to seek forgiveness" , "Forgive the polite interruption" , "Polite expression of regret, please excuse" , ""I'm sorry, could you say that again?"" .)