The most common and most likely answer to this crossword clue is the 7 letter word NAPHTHA
I've seen this crossword clue in Independent
N
A
P
H
T
H
A
More clues leading to the result NAPHTHA
- Sweep up last of slush that briefly forms solvent
- Flammable liquid ruined hat after hot vessel tipped over
- Oil container lifted – hot that, mostly!
- Search over — hard hat cracks hydrocarbon
- Mixture of sodium, phosphorus and hydrogen; hat dissolves in the solvent
- Sleep hard, that’s mostly chemical
- Dangerous liquid offered by new Australian pub that doesn’t close
- Oil reportedly tasteless? Mostly that
Buddy explains!

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 NAPHTHA mean?
NAPHTHA noun- Naturally occurring liquid petroleum.
- Any of a wide variety of aliphatic or aromatic liquid hydrocarbon mixtures distilled from petroleum or coal tar, especially as used in solvents or petrol.