The most common and most likely answer to this crossword clue is the 5 plus 4 letter word ROBIN HOOD
I've seen this crossword clue in Financial Times
R
O
B
I
N
H
O
O
D
More clues leading to the result ROBIN HOOD
- His band shot to fame where Isherwood lost his head
- Folk hero is to steal, wearing mask
- Old thief to steal trendy headgear
- Serial criminal cross about spike up on house
- Legendary thief to do what he does wearing head covering
- Cross to receive bishop in house of famous outlaw
- Outlaw what mugger might do to conceal himself
- Thug overcome by bird, his men drunk?
- Brazilian footballer’s extremely overrated as folk hero
- Much associated with this legendary outlaw
Buddy explains!
The straight part
We know that "Legendary thief" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case legendary thief = robin hood.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.