Black cat's in a frenzy (7)
I believe the answer is:
satanic
'black' is the definition.
(thesaurus)
'cat's in a frenzy' is the wordplay.
'frenzy' indicates an anagram.
'cats'+'in'+'a'='catsina'
'catsina' anagrammed gives 'SATANIC'.
(Other definitions for satanic that I've seen before include "Supremely evil" , "Like hell it is" , "Bad" , "Devil-like" , "like Mephisto" .)