The most common and most likely answer to this crossword clue is the 6 letter word FLATUS
I've seen this crossword clue in The Guardian
F
L
A
T
U
S
More clues leading to the result FLATUS
- Wind in plain to the west side of America
- Wind from America behind plane
- Release of this undesirable unlikely, initially confined to accommodation in block?
- Not bubbling, American gas
- Wind out of tune with middle section of percussion
- Gas faults in need of repair
- Dull American wind
- Wind not inspiring the States
Buddy explains!

The straight part
We know that "gas" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gas = flatus.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 FLATUS mean?
FLATUS noun- Gas generated in the digestive tract.
- Expulsion of such gas through the anus.
- Morbid inflation or swelling.