The most common and most likely answer to this crossword clue is the 9 letter word DANGEROUS
I've seen this crossword clue in The Guardian
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More clues leading to the result DANGEROUS
- Threatening fury in party over United States
- Day a surgeon flapped, posing risk
- Treacherous rogues and rebels
- Such a dog may be put down as hairy
- Organ used in transplant that’s unsafe
- It’s risky showing emotion during party with us
- Fury in party with American threatening
- Groans due to mangle becoming unsafe
- Almost put out admitting temper is reckless
- Menacing American appears at the end of party full of rage
Buddy explains!

The straight part
We know that "Such a dog may be put down/hairy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case such a dog may be put down/hairy = dangerous.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 DANGEROUS mean?
DANGEROUS adjective- Full of danger.
- Causing danger; ready to do harm or injury.
- In a condition of danger, as from illness; threatened with death.
- Hard to suit; difficult to please.
- Reserved; not affable.