Very large pot for boiling (8)
I believe the answer is:
cauldron
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very large pot for boiling</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for cauldron that I've seen before include "Large cooking pot" , "A large deep pot for boiling things" , "Very large metal pot for boiling" , "Place that's seething" , "Witches' vessel" .)