The most common and most likely answer to this crossword clue is the 11 letter word DEFLOWERING
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The straight part
We know that "loss of honour" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case loss of honour = deflowering.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 DEFLOWERING mean?
DEFLOWERING verb- To take the virginity of (somebody), especially a woman or girl.
- To deprive of flowers.
- To deprive of grace and beauty.
- The breaking of the hymen of a virgin.