Raced to fire rifle (7)
I believe the answer is:
ransack
'rifle' is the definition.
('ransack' can be a synonym of 'rifle')
'raced to fire' is the wordplay.
'raced' becomes 'ran' ('run' can be a synonym of 'race').
'to fire' becomes 'sack' ('sack' can be a synonym of 'fire').
'ran'+'sack'='RANSACK'
(Other definitions for ransack that I've seen before include "Search thoroughly - pillage" , "Rummage, rifle" , "Plunder; search ruthlessly" , "Go through a place causing damage and stealing things" , "Rob and despoil" .)