Sweltering (6)
I believe the answer is:
sultry
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sweltering</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sultry that I've seen before include "Passionate" , "Close -- sensual" , "Oppressively humid - sensual" , "Hot and steamy" , "Humid and oppressive" .)