Get angry about loud firearm (5)
I believe the answer is:
rifle
'firearm' is the definition.
(I know that rifle is a type of firearm)
'get angry about loud' is the wordplay.
'get angry' becomes 'rile' (to rile someone is to make them angry).
'about' indicates putting letters inside.
'loud' becomes 'f' (short for forte - 'loud' in music).
'rile' enclosing 'f' is 'RIFLE'.
(Other definitions for rifle that I've seen before include "An arm" , "Ransack; a weapon" , "shoot?" , "One that has stock" , "Weapon - sack" .)