Harsh — radical (7)
I believe the answer is:
drastic
I believe this is a double definition.
'harsh' is the first definition.
(thesaurus)
'radical' is the second definition.
(drastic can mean radical or extreme)
(Other definitions for drastic that I've seen before include "'Dramatic, extreme (7)'" , "Severe and far-reaching" , "Very severe or serious" , "Severe, radical (measures)" , "Extremely severe" .)