The most common and most likely answer to this crossword clue is the 7 letter word AMMONIA
I've seen this crossword clue in The Guardian
A
M
M
O
N
I
A
More clues leading to the result AMMONIA
- Pungent gas shells etc in back area
- Shells, perhaps, put back in a cleansing solution
- After what's in magazine, great new twists? It's a gas
- More inclined to grumble, we hear, after Mam’s first let off gas
- Before noon I moan, ordered to get cleaning fluid
- Piece of gammon I ate, resulting in pungent gas
- What’s in a magazine and in a novel is pungent stuff
- What weapons might contain in a dodgy compound?
- Egyptian deity — one with a strong nose
- Smelly gas in the morning giving more grief if audible
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 AMMONIA mean?
AMMONIA noun- A gaseous compound of hydrogen and nitrogen, NH3, with a pungent smell and taste.
- A solution of this compound in water used domestically as a cleaning fluid.