The most common and most likely answer to this crossword clue is the 8 letter word BANNERET
I've seen this crossword clue in The Times
B
A
N
N
E
R
E
T
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 = banneret.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 BANNERET mean?
BANNERET noun- A noble, knighted feudal lord who has the right to lead his vassals to battle under his own banner
- A small banner.
- A proposed but unadopted senior commissioned rank of the Royal Air Force equivalent to group captain.
- A civil officer in some Swiss cantons.