No rating could be so uneducated (8)
I believe the answer is:
ignorant
'uneducated' is the definition.
(similar in meaning)
'no rating could be' is the wordplay.
'could be' indicates an anagram.
'no'+'rating'='norating'
'norating' with letters rearranged gives 'IGNORANT'.
'so' is the link.
(Other definitions for ignorant that I've seen before include "Ill-mannered" , "Illiterate - unaware" , "Unaware, uninformed" , "Crass" , "Without knowledge" .)