Pure evil's awfully disgusting (9)
I believe the answer is:
repulsive
'disgusting' is the definition.
(thesaurus)
'pure evil's awfully' is the wordplay.
'awfully' indicates anagramming the letters.
'pure'+'evils'='pureevils'
'pureevils' is an anagram of 'REPULSIVE'.
(Other definitions for repulsive that I've seen before include "Abhorrent" , "Obnoxious" , "Offensive" , "Disgusting" , "ugly" .)