Detest dreadful heat (4)
I believe the answer is:
hate
'detest' is the definition.
(synonyms)
'dreadful heat' is the wordplay.
'dreadful' is an anagram indicator.
'heat' anagrammed gives 'HATE'.
(Other definitions for hate that I've seen before include "Passionately dislike" , "Intense emotion opposite to love" , "Abominate" , "[OPPOSITE OF] Be besotted with" , "powerful emotion" .)