The most common and most likely answer to this crossword clue is the 11 letter word EXONERATION
I've seen this crossword clue in The Sunday Telegraph
E
X
O
N
E
R
A
T
I
O
N
More clues leading to the result EXONERATION
Buddy explains!

The straight part
We know that "forgiveness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case forgiveness = exoneration.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EXONERATION mean?
EXONERATION noun- An act of disburdening, discharging, or freeing morally from a charge or imputation.
- The state of being disburdened or freed from a charge.