Turned out stupidly illiterate (9)
I believe the answer is:
untutored
'illiterate' is the definition.
(thesaurus)
'turned out stupidly' is the wordplay.
'stupidly' indicates an anagram.
'turned'+'out'='turnedout'
'turnedout' with letters rearranged gives 'UNTUTORED'.
(Other definitions for untutored that I've seen before include "without formal education" , "Not taught" , "lacking refinement" , "lacking education" , "Being ignorant" .)