Cardinal providing article about Religious Education (5)
I believe the answer is:
three
'cardinal' is the definition.
('three' can be similar in meaning to 'cardinal')
'article about religious education' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech**).
'about' means one lot of letters goes inside another.
'religious education' becomes 're'.
'the' enclosing 're' is 'THREE'.
'providing' is the link.
(Other definitions for three that I've seen before include "Number of Dumas's musketeers" , "Bears or blind mice" , "Number of times N appears in this completed grid" , "Cardinal number" , "Square root of nine" .)