Pirate or bandit (6)
I believe the answer is:
raider
I believe this is a double definition.
'pirate' is the first definition.
(I've seen this in another clue)
'bandit' is the second definition.
(thesaurus)
(Other definitions for raider that I've seen before include "looter" , "Depredator" , "One who makes surprise attack, perhaps to steal" , "One making incursion" , "One making a rapid surprise attack" .)