The most common and most likely answer to this crossword clue is the 9 letter word AMETHYSTS
I've seen this crossword clue in The Guardian
A
M
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T
H
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More clues leading to the result AMETHYSTS
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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 AMETHYSTS mean?
AMETHYSTS noun- A transparent purple variety of quartz, used as a gemstone.
- A purple colour.
- The purple tincture when emblazoning the arms of the English nobility.