A republican badly hurt legendary king (6)
I believe the answer is:
arthur
'legendary king' is the definition.
(I've seen this before)
'a republican badly hurt' is the wordplay.
'republican' becomes 'r' (abbreviation).
'badly' indicates an anagram.
'hurt' with letters rearranged gives 'thur'.
'a'+'r'+'thur'='ARTHUR'
(Other definitions for arthur that I've seen before include "(Legendary?) English king" , "Legendary British king" , "- - Lowe (actor)" , "Camelot's king" , "Old king" .)