Report of army stockpile (5)
I believe the answer is:
hoard
'stockpile' is the definition.
(I've seen this before)
'report of army' is the wordplay.
'report of' indicates a 'sounds like' (homophone) clue.
'army' becomes 'horde' (I've seen this before).
'horde' sounds like 'HOARD'.
(Other definitions for hoard that I've seen before include "Rhoda (anag.)" , "Store of treasure" , "Secret store of valuables" , "Store of money or valuables" , "Store, usually hidden" .)