The most common and most likely answer to this crossword clue is the 9 letter word SCUFFLING
I've seen this crossword clue in The Daily Telegraph
S
C
U
F
F
L
I
N
G
Buddy explains!

The straight part
We know that "fighting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fighting = scuffling.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 SCUFFLING mean?
SCUFFLING verb- To fight or struggle confusedly at close quarters.
- To walk with a shuffling gait.
- To make a living with difficulty, getting by on a low income, to struggle financially.
- A confused struggle