Correct religious education class (6)
I believe the answer is:
reform
'correct' is the definition.
(thesaurus)
'religious education class' is the wordplay.
'religious education' becomes 'RE' (abbreviation).
'class' becomes 'form' (synonyms).
're'+'form'='REFORM'
(Other definitions for reform that I've seen before include "Change one's ways (for the better?)" , "Go straight" , "Mend one's ways" , "Removal of abuses" , "Correct(ion of) abuses" .)