Rim, lip of a cup (4)
I believe the answer is:
brim
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">rim</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">lip of a cup</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for brim that I've seen before include "Top edge of a container" , "Edge around a hat" , "Circumference" , "Upper edge" , "Projecting edge of hat" .)