Royal Marine in A&E died with weapon (5)
I believe the answer is:
armed
'with weapon' is the definition.
'royal marine in ae died' is the wordplay.
'royal marine' becomes 'RM' (abbreviation).
'in' indicates putting letters inside.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'rm' inserted within 'ae' is 'arme'.
'arme'+'d'='ARMED'
(Other definitions for armed that I've seen before include "prepared to shoot?" , "Supplied with weapons" , "equipped for fighting" , "Bearing weapons" , "Provided with weapons" .)