The most common and most likely answer to this crossword clue is the 7 letter word COMBATS
I've seen this crossword clue in The Daily Telegraph
C
O
M
B
A
T
S
Buddy explains!

The straight part
We know that "Fights" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fights = combats.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 COMBATS mean?
COMBATS noun- A battle, a fight (often one in which weapons are used).
- A struggle for victory
- To fight; to struggle against.
- To fight (with); to struggle for victory (against).