The most common and most likely answer to this crossword clue is the 6 letter word KUMITE
K
U
M
I
T
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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 = kumite.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 KUMITE mean?
KUMITE noun- The aspect of karate in which a person trains against an adversary, using the techniques learned from the kihon and kata.