Picture of legendary king (6)
I believe the answer is:
arthur
'legendary king' is the definition.
(King Arthur)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for arthur that I've seen before include "Husband of Guinevere" , "Old king" , "Owner of Excalibur" , "See 21" , ""The once and future king"" .)