The most common and most likely answer to this crossword clue is the 10 letter word INDULGENCE
I've seen this crossword clue in The Daily Telegraph
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The straight part
We know that "Pardon" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pardon = indulgence.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 INDULGENCE mean?
INDULGENCE noun- The act of indulging
- Tolerance
- Catering to someone's every desire
- Something in which someone indulges
- An indulgent act; favour granted; gratification.
- A pardon or release from the expectation of punishment in purgatory, after the sinner has been granted absolution.
- (Roman Catholic Church) to provide with an indulgence