Hastened to fire rifle (7)
I believe the answer is:
ransack
'rifle' is the definition.
('ransack' can be a synonym of 'rifle')
'hastened to fire' is the wordplay.
'hastened' becomes 'ran' (I've seen this before).
'to fire' becomes 'sack' ('sack' can be a synonym of 'fire').
'ran'+'sack'='RANSACK'
(Other definitions for ransack that I've seen before include "Pillage, plunder" , "Search (a place) thoroughly" , "Search thoroughly and destructively" , "Search thoroughly and roughly" , "Plunder - rummage" .)