Horrid and terribly evil (4)
I believe the answer is:
vile
'horrid' is the definition.
(thesaurus)
'terribly evil' is the wordplay.
'terribly' indicates an anagram.
'evil' is an anagram of 'VILE'.
'and' acts as a link.
(Other definitions for vile that I've seen before include "Book by Evelyn Waugh" , "Cheap; shameful" , "Live (anag.)" , "Despicable in evil way" , "Loathsome - draw veil over it" .)