Single item of ammunition (4)

I believe the answer is:

unit

'single item' is the definition.
(I've seen this before)

'of ammunition' is the wordplay.
'of' says the answer is hidden in the clue.
'UNIT' is hidden in the letters of 'ammunition'.

(Other definitions for unit that I've seen before include "Single item; one" , "Element or part" , "Entity making up part of a whole" , "Specialised group" , "Separate part" .)

I've seen this clue in The Independent.

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.