The most common and most likely answer to this crossword clue is the 10 letter word SUBVERSION
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result SUBVERSION
Buddy explains!
The straight part
We know that "ruin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ruin = subversion.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 SUBVERSION mean?
SUBVERSION noun- The act of subverting or the condition of being subverted.
- A systematic attempt to overthrow a government by working from within; undermining.
- A revision considered more similar to preceding subversions than a revision deemed a new "version" is to preceding versions.