In religious education improperly repeat witticism (8)
I believe the answer is:
repartee
'witticism' is the definition.
(I know that repartee is a type of witticism)
'in religious education improperly repeat' is the wordplay.
'in' is an insertion indicator.
'religious education' becomes 'RE' (abbreviation).
'improperly' indicates anagramming the letters (I've seen this in other clues).
'repeat' is an anagram of 'eparte'.
're' placed around 'eparte' is 'REPARTEE'.
(Other definitions for repartee that I've seen before include "Ready and witty retort" , "Witty and rapid conversation" , "Clever or witty rejoinder" , "Sparkling conversation" , "Series of clever replies" .)