Feel uncomfortably hot (7)
I believe the answer is:
swelter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">feel uncomfortably hot</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 swelter that I've seen before include "Endure great heat" , "Be too hot; Gormenghast chef" , "Sweat and feel faint" , "Feel uncomfortably hot" , "Suffer oppressive heat" .)