The most common and most likely answer to this crossword clue is the 5 plus 6 letter word CROSS SWORDS
I've seen this crossword clue in The Guardian
C
R
O
S
S
S
W
O
R
D
S
More clues leading to the result CROSS SWORDS
- Argue, getting stuck initially in puzzles like this one
- Our love bites sweet, initially — disagree?
- Argue puzzles must include smut?
- Puzzles about son’s dispute
- Argue with son into puzzles
- In our bag you’ll find small spar
- Fight with minimum of satisfaction to fill in these?
- A violent exchange with second in duel
- Enter into dispute about beginning to solve puzzles
- Bridge player engrossed by word games causes quarrel
Buddy explains!
The straight part
We know that "Duel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case duel = cross swords.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.