The most common and most likely answer to this crossword clue is the 6 letter word ETHENE
E
T
H
E
N
E
More clues leading to the result ETHENE
- Leave the neighbouring housing compound
- Extracted from mine, the necessary chemical
- Flammable gas in use? Then evacuate!
- Eight initially, followed by the same number
- Chemical leaking from receptacle then explodes
- Description of centre for unfreezing ethylene
- Some inhale, then exhale an anaesthetic
- Gas inside the new bottle
- She then extracts partly unsaturated hydrocarbon
- ...one then extracts some organic chemical
Buddy explains!

The straight part
We know that "number" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case number = ethene.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 ETHENE mean?
ETHENE noun- (IUPAC name) The organic chemical compound ethylene. The simplest alkene, a colorless gaseous (at room temperature and pressure) hydrocarbon with the chemical formula C2H4
- Any alkene derived from ethylene