Close, muggy (5)
I believe the answer is:
humid
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">close</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">muggy</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for humid that I've seen before include "Sultry" , "'Moist, damp (5)'" , "Moist, warm (weather)" , "Muggy" , "Damp and warm" .)