Storage tank (9)
I believe the answer is:
reservoir
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">storage tank</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that reservoir is a type of storage tank)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for reservoir that I've seen before include "Lake for collecting and storing water" , "River rose (anag.)" , "Lake used to store water for community use" , "Store for water etc" , "Area for storage, of water say" .)