The most common and most likely answer to this crossword clue is the 9 letter word DECIMATED
I've seen this crossword clue in The Guardian
D
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Buddy explains!
The straight part
We know that "Killed many" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case killed many = decimated.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 DECIMATED mean?
DECIMATED verb- To kill one-tenth of a group, (specifically) as a military punishment in the Roman army selected by lot, usually carried out by the surviving soldiers.
- To destroy or remove one-tenth of anything.
- To devastate: to reduce or destroy significantly but not completely.
- To exact a tithe or other 10% tax
- To tithe: to pay a 10% tax.
- To decimalize: to divide into tenths, hundredths etc.
- To reduce to one-tenth: to destroy or remove nine-tenths of anything.
- To replace a high-resolution model with another of lower but acceptable quality.