Uneducated thug - a nut, crazy (8)
I believe the answer is:
untaught
'uneducated' is the definition.
(similar in meaning)
'thug a nut crazy' is the wordplay.
'crazy' is an anagram indicator.
'thug'+'a'+'nut'='thuganut'
'thuganut' is an anagram of 'UNTAUGHT'.
(Other definitions for untaught that I've seen before include "Not tutored or instructed" , "Not acquired by education" , "having learnt nothing?" , "excluded from class?" , "spontaneous" .)