The hot weather bothers Thea (4)
I believe the answer is:
heat
'the hot weather' is the definition.
'bothers thea' is the wordplay.
'bothers' indicates anagramming the letters (I've seen 'bothered' mean this).
'thea' is an anagram of 'HEAT'.
(Other definitions for heat that I've seen before include "Preliminary round in a contest" , "Energy that causes a rise in temperature" , "Vehemence" , "Warmth - gossip mag" , "Warmth - passion" .)