Things that can kill animal in retreat (4)

I believe the answer is:

gats

'things that can kill' is the definition.
(informal term for pistols)

'animal in retreat' is the wordplay.
'animal' becomes 'stag' (I've seen this before).
'in retreat' is a reversal indicator.
'stag' back-to-front is 'GATS'.

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.