Prudish play on words about girl being educated (7)
I believe the answer is:
puritan
'prudish' is the definition.
(thesaurus)
'play on words about girl being educated' is the wordplay.
'play on words' becomes 'pun' ('pun' can be a synonym of 'play on words').
'about' means one lot of letters goes inside another.
'girl being educated' becomes 'rita' (character from the film Educating Rita).
'pun' placed around 'rita' is 'PURITAN'.
(Other definitions for puritan that I've seen before include "Strait-laced" , "Calvinist Protestant" , "Train up (anag.)" , "Person of censorious moral beliefs" , "Strictly moral person" .)