The most common and most likely answer to this crossword clue is the 8 letter word TOMAHAWK
T
O
M
A
H
A
W
K
More clues leading to the result TOMAHAWK
- Beastly male with an aggressor's weapon
- Axe meant for academic to sell
- Male, warlike type, holding a chopper
- Group of Norwegians work on, say, Cruise Missile?
- Weapon made by boy, no dove
- Male, a belligerent killer on reservation?
- Axe a likely Trump ally after pussy?
- Weapon — but isn’t Jerry a pacifist?
- Betweeen cat and bird, a weapon
- Cruise, perhaps, a belligerent sort of weapon
Buddy explains!

The straight part
We know that "Killer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case killer = tomahawk.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TOMAHAWK mean?
TOMAHAWK noun- An ax used by Native American warriors.
- A dunk in which the person dunking the ball does so with his arm behind his head.
- A geometric construction consisting of a semicircle and two line segments that serves as a tool for trisecting an angle; so called from its resemblance to the American Indian axe.
- A field hockey shot style that involves a player turning their hockey stick upside-down and swinging it so that its inside edge will come into contact with the ball.
- To strike with a tomahawk.