Barrel, tank (3)
I believe the answer is:
vat
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">barrel</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">tank</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for vat that I've seen before include "Large tank; purchase tax" , "possible source of liquid" , "Container for liquids" , "Large vessel for storing liquids and a large tax" , "subject of 17, 8 [CHANCELLORS STATEMENT]" .)