Aver bias, terribly harsh (8)
I believe the answer is:
abrasive
'harsh' is the definition.
(I've seen this before)
'aver bias terribly' is the wordplay.
'terribly' is an anagram indicator.
'aver'+'bias'='averbias'
'averbias' is an anagram of 'ABRASIVE'.
(Other definitions for abrasive that I've seen before include "One that wears" , "Caustic, harsh" , "Harsh - chafing" , "Harsh in manner, capable of causing anger" , "Rough, irritating" .)