Reveals how to get into Sunday school (5)
I believe the answer is:
shows
'reveals' is the definition.
('show' can be a synonym of 'reveal')
'how to get into sunday school' is the wordplay.
'to get into' is an insertion indicator.
'sunday' becomes 's'.
'school' becomes 'S'.
's'+'s'='ss'
'how' placed inside 'ss' is 'SHOWS'.
(Other definitions for shows that I've seen before include "entertainment" , "Exhibitions" , "Demonstrates the musicals?" , "Turns up" , "Exhibits" .)