Unusually hot, stormy and exhausting (8)
I believe the answer is:
thorough
'exhausting' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I can't see?
'unusually hot stormy' is the wordplay.
'unusually' indicates an anagram.
'stormy' becomes 'rough' (similar in meaning).
'hot' anagrammed gives 'tho'.
'tho'+'rough'='THOROUGH'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for thorough that I've seen before include "Painstakingly careful and accurate" , "Assiduous, painstaking" , "Painstaking; absolute" , "Doing things with great attention to detail" , "Leaving no stone unturned" .)