The most common and most likely answer to this crossword clue is the 8 letter word BUTCHERS
I've seen this crossword clue in The Daily Telegraph
B
U
T
C
H
E
R
S
Buddy explains!

The straight part
We know that "kills" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case kills = butchers.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 BUTCHERS mean?
BUTCHERS noun- A person who prepares and sells meat (and sometimes also slaughters the animals).
- A brutal or indiscriminate killer.
- (from butcher's hook) A look.
- A person who sells candy, drinks, etc. in theatres, trains, circuses, etc.
- To slaughter (animals) and prepare (meat) for market.
- To kill brutally.
- To ruin (something), often to the point of defamation.
- A butcher’s shop
- A look (short form of butcher's hook)