Wide-mouthed cup (6)
I believe the answer is:
beaker
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wide-mouthed cup</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 beaker that I've seen before include "Plastic mug" , "Glass container in a laboratory" , "Glass vessel" , "Tall cup or tumbler" , "Wide-mouthed cup" .)