Large fish tank (8)
I believe the answer is:
aquarium
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">large fish tank</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for aquarium that I've seen before include "Tank for aquatic life" , "A kind of fish zoo" , "Building containing fish tanks" , "Large fish tank" , "Building containing live fish for display" .)