Cove or bay (5)
I believe the answer is:
inlet
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">cove</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">bay</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for inlet that I've seen before include "Entry port" , "Opening through which fluid can pass" , "bit of a lake here?" , "Small area of sea" , "Arm of lake, river" .)