The most common and most likely answer to this crossword clue is the 11 letter word PENITENTIAL
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result PENITENTIAL
Buddy explains!
The straight part
We know that "Showing remorse" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case showing remorse = penitential.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 PENITENTIAL mean?
PENITENTIAL noun- A book or set of rules pertaining to the Christian sacrament of penance
- Pertaining to penance or penitence