The most common and most likely answer to this crossword clue is the 6 letter word GAWAIN
I've seen this crossword clue in Independent
G
A
W
A
I
N
More clues leading to the result GAWAIN
- Knight's advance across wide area
- Round Table member finds cart carrying the heads of Guinevere and Arthur
- Success capturing a Welsh knight
- Legendary nobleman‘s legacy? ‘Twas mine, in essence
- Knight to run faster to embrace a woman
- Georgia on the wagon with knight
- A jester somersaulting over popular knight
- A wife in addition for knight
Buddy explains!

The straight part
We know that "knight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case knight = gawain.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.