The most common and most likely answer to this crossword clue is the 9 letter word VIS-A-VIS
I've seen this crossword clue in The Times
V
I
S
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A
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V
I
S
More clues leading to the result VIS-A-VIS
Buddy explains!

The straight part
We know that "concerning" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case concerning = vis-a-vis.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 VIS-A-VIS mean?
VIS-A-VIS noun- A small horse-drawn carriage for two people sitting facing each other.
- A sofa with seats for two people, so arranged that the occupants are face to face while sitting on opposite sides.
- One of two (or more) people facing or opposite each other.
- A date or escort in a social event.
- A person holding a corresponding position in another organisation.
- Face-to-face
- In relation to
- (of a coin) having two portraits facing each other
- Face to face (with another)
- In a position facing a specified or implied subject.
- In relation to; compared with.
- Opposite, across from, set so as to be facing.