The most common and most likely answer to this crossword clue is the 9 letter word RELIEVERS
I've seen this crossword clue in Financial Times
R
E
L
I
E
V
E
R
S
More clues leading to the result RELIEVERS
Buddy explains!
The straight part
We know that "What asthmatic carries about" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what asthmatic carries about = relievers.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 RELIEVERS mean?
RELIEVERS noun- Something which relieves (pain, etc.).
- A relief pitcher.
- Someone who fills in for another.
- A garment kept for being lent out.