Answer:

ninja

Answer	Crossword Clue
NINJA	Japanese mercenary
NINJA	Stealthy spy, perhaps
NINJA	Part of TMNT

NINJA	Dark-clad warrior
NINJA	Agent in black
NINJA	Figure of stealth
NINJA	Ancient mercenary
NINJA	Stealthy Easterner
NINJA	Tenchu video game series hero
NINJA	Teenage turtle of comics
NINJA	Martial arts mercenary

NINJA	Common video game fighter
NINJA	One of a reptilian comics quartet
NINJA	"Teenage Mutant ... Turtles"
NINJA	Assassin in many martial arts films
NINJA	Silent assassin
NINJA	Stealthy Japanese agent
NINJA	Masked assassin
NINJA	Shuriken thrower

NINJA	Asian assassin
NINJA	Black Halloween costume
NINJA	Covert agent in Asia
NINJA	Elusive warrior
NINJA	Certain warrior
NINJA	Kusarigama wielder
NINJA	Black-clad assassin
NINJA	Masked warrior

NINJA	Feudal Japanese mercenary
NINJA	Turtle in a 2014 film
NINJA	Japanese assassin
NINJA	Teenage Mutant .. Turtles
NINJA	Shogun's warrior
NINJA	Shogun's spy
NINJA	Black-garbed mercenary
NINJA	Mercenary of yore

NINJA	Kyoto killer
NINJA	Ancient Japanese mercenary
NINJA	Stealthy assassin
NINJA	Japanese sneaker?
NINJA	User of a star-shaped weapon called a shuriken