The most common and most likely answer to this crossword clue is the 9 letter word ACETYLENE
I've seen this crossword clue in The Guardian
A
C
E
T
Y
L
E
N
E
More clues leading to the result ACETYLENE
- Extraordinary – topless way of dressing on Tyneside is a gas
- Eyelet can deploy dangerous gas
- Gas from wicked, heartless Tory, poor in speech
- Wrongly elect any European leader? That’s inflammatory
- Expert emptied tray with inadequate-sounding fuel for torch
- Cool-temperature heavy fuel ultimately bearing flammable gas
- Excited girl leaving energetically for dancing — a gas!
- A: Let Yen's adjustment become explosive material
- One outlet — with yen you get gas
- Elect any bumbling imbecile? Ultimately, that’s a gas!
Buddy explains!
The straight part
We know that "dangerous gas" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dangerous gas = acetylene.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 ACETYLENE mean?
ACETYLENE noun- Any organic compound having one or more carbon–carbon triple bonds; an alkyne.
- Ethyne; the simplest alkyne, a hydrocarbon of formula HC≡CH. It is a colourless, odorless gas, formerly used as an illuminating gas, but now used in welding or metallurgy.
- A lamp powered by acetylene, particularly a motor vehicle headlight.