Armories (8)
I believe the answer is:
arsenals
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">armories</span>' is the definition.<br/ ><span class="explanation-format__explanation">('arsenal' can be a synonym of 'armory')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for arsenals that I've seen before include "Collections of arms and ammunition" , "Arms depots" .)