The most common and most likely answer to this crossword clue is the 7 plus 2 plus 4 letter word PASSAGE OF ARMS
I've seen this crossword clue in The Guardian
P
A
S
S
A
G
E
O
F
A
R
M
S
More clues leading to the result PASSAGE OF ARMS
Buddy explains!
The straight part
We know that "a fight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a fight = passage of arms.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.