The most common and most likely answer to this crossword clue is the 8 letter word DUELLIST
I've seen this crossword clue in Independent
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More clues leading to the result DUELLIST
- One might have a second, outstanding, large register
- Second employer
- Who aims to settle a dispute?
- Fighter that ought to be paid still in action
- Honourable combatant
- One seeking satisfaction with second helping
- Fighter that’s outstanding, large and lean
- Contestant's outstanding, still to be trained
- One seeking satisfaction coming with large inventory …
- Outstanding learner takes on lean combatant
Buddy explains!

The straight part
We know that "combatant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case combatant = duellist.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 DUELLIST mean?
DUELLIST noun- A person who fights a duel.