Japanese combatant seen in jazzy trousers (5)
I believe the answer is:
ninja
'japanese combatant' is the definition.
(type of Japanese warrior)
'seen in jazzy trousers' is the wordplay.
'trousers' indicates a hidden word (trouser can mean to steal or take).
'NINJA' can be found hidden inside 'seen in jazzy'.
(Other definitions for ninja that I've seen before include "One who steals" , "Japanese trained assassin" , "Teenage Mutant -- Turtles (TV/film)" , "Practioner of ninjitsu" , "Japanese assassin/spy" .)