Recoiling part of gunpowder-based cavalry weapon (5)
I believe the answer is:
sabre
'weapon' is the definition.
(sabre is a kind of weapon)
'recoiling part of gunpowder-based cavalry' is the wordplay.
'recoiling' says the letters should be written in reverse.
'part of' indicates a hidden word.
'erbas' is hidden in the letters of 'gunpowder based cavalry'.
'erbas' in reverse letter order is 'SABRE'.
(Other definitions for sabre that I've seen before include "Type of sword" , "Bares (anag.)" , "Heavy cavalry sword" , "Walt --, cartoonist" , "Sword with curved blade" .)