The most common and most likely answer to this crossword clue is the 8 letter word SCUPPERS
I've seen this crossword clue in The Daily Telegraph
S
C
U
P
P
E
R
S
Buddy explains!

The straight part
We know that "Ruins" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ruins = scuppers.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 SCUPPERS mean?
SCUPPERS noun- A drainage hole on the deck of a ship.
- A similar opening in a wall or parapet that allows water to drain from a roof.
- Thwart or destroy, especially something belonging or pertaining to another; compare scuttle.