Terribly evil and horrid (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' is the link.
(Other definitions for vile that I've seen before include "Cheap; shameful" , "Revolting" , "Detestable" , "Loathsome - draw veil over it" , "Depraved" .)