Ancient marauder (3)
I believe the answer is:
hun
'ancient marauder' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hun that I've seen before include "One of Attila's people" , "Warlike nomad" , "Attila the ... invaded Europe in 5th century" , "Eg, Attila" , "Warlike invader" .)