Train up wayward moralist (7)
I believe the answer is:
puritan
'moralist' is the definition.
(I've seen this before)
'train up wayward' is the wordplay.
'wayward' indicates anagramming the letters.
'train'+'up'='trainup'
'trainup' anagrammed gives 'PURITAN'.
(Other definitions for puritan that I've seen before include "narrow-minded" , "Person of censorious moral beliefs" , "Strictly moral person" , "Train up (anag.)" , "Dour Protestant" .)