The most common and most likely answer to this crossword clue is the 10 letter word CONCERNING
I've seen this crossword clue in The Daily Telegraph
C
O
N
C
E
R
N
I
N
G
More clues leading to the result CONCERNING
Buddy explains!

The straight part
We know that "Dealing with/worrying" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dealing with/worrying = concerning.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 CONCERNING mean?
CONCERNING verb- To relate or belong to; to have reference to or connection with; to affect the interest of; to be of importance to.
- To engage by feeling or sentiment; to interest.
- To make somebody worried.
- That which one is concerned in; one's business.
- Causing concern; worrisome.
- Important.
- Regarding, respecting.