The most common and most likely answer to this crossword clue is the 10 letter word ABDICATION
I've seen this crossword clue in Financial Times
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Buddy explains!
The straight part
We know that "a possible end for a monarchy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a possible end for a monarchy = abdication.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 ABDICATION mean?
ABDICATION noun- The act of disowning or disinheriting a child.
- The act of abdicating; the renunciation of a high office, dignity, or trust, by its holder.
- The voluntary renunciation of sovereign power
- The renunciation of interest in a property or a legal claim; abandonment.
- The action of being deposed from the seat of power.