Ordnance depot (7)
(Other definitions for arsenal that I've seen before include "Store of guns and ammunition" , "Eleven" , "Football team - magazine" , "Mil. magazine; FA club" , "Football club and military store" .)
'ordnance depot' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for armoury that I've seen before include "Arsenal - magazine" , "Weapons store" , "Collection of weapons" , "Means" , "Ordnance depot" .)