Illustration in a new church includes saint (8)
I believe the answer is:
instance
'illustration' is the definition.
(I've seen this before)
'in a new church includes saint' is the wordplay.
'a new' becomes 'an' (I've seen this in other clues**).
'church' becomes 'ce' (abbreviation for Church of England).
'includes' is an insertion indicator.
'saint' becomes 'st'.
'in'+'an'+'ce'='inance'
'inance' placed around 'st' is 'INSTANCE'.
(Other definitions for instance that I've seen before include "Case in point" , "Particular example" , "Occasion" , "Cite as an example" , "Particular case; cite" .)