Cardinal possibly raised double gun (9)
I believe the answer is:
derringer
'gun' is the definition.
(I know that Derringer is a type of pistol)
'cardinal possibly raised double' is the wordplay.
'cardinal possibly' becomes 'red' (cardinal is a kind of red).
'raised' shows that the letters should be reversed in order (going up in a down clue).
'double' becomes 'ringer' (I've seen this before).
'red' reversed gives 'der'.
'der'+'ringer'='DERRINGER'
(Other definitions for derringer that I've seen before include "Pocket pistol" , "Short-barrelled American pistol" , "Weapon" , "Small pistol used by gamblers in western films" .)