Leader of the Huns (6)
I believe the answer is:
attila
'leader of the huns' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for attila that I've seen before include "Fifth century king of the Huns" , "Well-known Hun" , "Brutal invader" , "The Scourge of God" , "Hunnish conqueror" .)