Suffer from heat (7)
I believe the answer is:
swelter
'suffer from heat' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for swelter that I've seen before include "Suffer oppressive heat" , "Be too hot; Gormenghast chef" , "Endure oppressive heat" , "Overheat" , "Be uncomfortably hot as in the sun" .)