Soldiers caper, stealing knight's weapons (8)
I believe the answer is:
ordnance
'weapons' is the definition.
(I've seen this before)
'soldiers caper stealing knight's' is the wordplay.
'soldiers' becomes 'OR' (Other Ranks).
'caper' becomes 'dance' (I've seen this in other clues).
'stealing' indicates putting letters inside.
'knight' becomes 'N' (chess abbreviation).
'dance' placed around 'n' is 'dnance'.
'or'+'dnance'='ORDNANCE'
(Other definitions for ordnance that I've seen before include "The Survey provides maps" , "Anne Cord is in military supplies" , "Survey may follow this" , "type of armament" , "regulation" .)