Biting Ivor, score badly (9)
I believe the answer is:
corrosive
'biting' is the definition.
(thesaurus)
'ivor score badly' is the wordplay.
'badly' is an anagram indicator (letters in the wrong order).
'ivor'+'score'='ivorscore'
'ivorscore' anagrammed gives 'CORROSIVE'.
(Other definitions for corrosive that I've seen before include "Destroying by chemical action" , "Hurtful" , "Caustic and destructive" , "Able to eat away" , "Caustic, erosive" .)