Hunnish leader (6)
I believe the answer is:
attila
'hunnish leader' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for attila that I've seen before include "The greatest Hun leader" , "King of the Huns, d. 453" , "First-century king of the Huns" , "5th century king of the Huns who sacked Rome" , "He attacked the Romans" .)