Soldiers requiring some ammunition (4)
I believe the answer is:
unit
'soldiers' is the definition.
(unit can mean a group of soldiers )
'some ammunition' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'UNIT' is hidden within 'ammunition'.
'requiring' is the link.
(Other definitions for unit that I've seen before include "Military team" , "One; military group" , "Single item, maybe part of a set" , "Army division" , "Single manufactured item; military grouping" .)