Weapon a gamekeeper has raised (4)
I believe the answer is:
epee
'weapon' is the definition.
(epee is a kind of weapon)
'a gamekeeper has raised' is the wordplay.
'has' says the answer is hidden in the clue.
'raised' says the letters should be written in reverse (going up in a down clue).
'eepe' is hidden within 'gamekeeper'.
'eepe' in reverse letter order is 'EPEE'.
(Other definitions for epee that I've seen before include "Duelling blade" , "Fencing sword similar to a foil" , "Fencer's weapon" , "Pointed weapon" , "Fencing weapon" .)