The most common and most likely answer to this crossword clue is the 9 letter word DISPUTING
I've seen this crossword clue in Independent
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More clues leading to the result DISPUTING
Buddy explains!

The straight part
We know that "Questioning" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case questioning = disputing.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 DISPUTING mean?
DISPUTING verb- To contend in argument; to argue against something maintained, upheld, or claimed, by another
- To make a subject of disputation; to argue pro and con; to discuss
- To oppose by argument or assertion; to controvert; to express dissent or opposition to; to call in question; to deny the truth or validity of
- To strive or contend about; to contest
- To struggle against; to resist
- Dispute; argument