Cannon or artillery (8)
I believe the answer is:
ordnance
This clue is a double definition.
'cannon' is the first definition.
(I've seen this in another clue)
'artillery' is the second definition.
(I know that artillery can be written as ordnance)
(Other definitions for ordnance that I've seen before include "Arsenal's big guns" , "The Survey provides maps" , "Anne Cord is in military supplies" , "Car on end (anag) - artillery" , "Mounted guns, cannon" .)