The most common and most likely answer to this crossword clue is the 9 letter word ARTHURIAN
I've seen this crossword clue in The Times
A
R
T
H
U
R
I
A
N
More clues leading to the result ARTHURIAN
- Two men in kingly legend
- Legendary heretic seizes day
- Skill leading German invader to adopt elevated attitude of British king
- Legendary British paintings mostly damaged by Scotsman
- Old king’s from day one into knitwear!
- Like some legends making us turn a hair, surprisingly
- The stuff of legend: from day one being seen in a sweater!
Buddy explains!
The straight part
We know that "Legendary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case legendary = arthurian.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.