Round Table king (6)
I believe the answer is:
arthur
'round table king' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arthur that I've seen before include "Owner of Excalibur" , "(Legendary?) English king" , "Legendary king of the Britons" , "See 21" , "Husband of Guinevere" .)