Japanese assassin (5)
I believe the answer is:
ninja
'japanese assassin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ninja that I've seen before include "Japanese expert in stealth and martial arts" , "Assassins" , "Assassin from Japan" , "Eastern agent" , "Medieval Japanese trained in martial arts, assassination and espionage" .)