Be too hot (7)
I believe the answer is:
swelter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be too 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 "Overheat" , "Suffer oppressive heat" , "Suffer when too hot" , "Endure oppressive heat" , "Be too hot; Gormenghast chef" .)