Notice American's ancestor in the church (4)
I believe the answer is:
adam
'ancestor in the church' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'notice american's' is the wordplay.
'notice' becomes 'ad' (short for advert).
'american' becomes 'Am' (abbreviation in some contexts).
'ad'+'am'='ADAM'
Can you help me to learn more?
(Other definitions for adam that I've seen before include "Eden man" , "Man No. 1" , "First person" , "According to the Bible, progenitor of the human race" , "one might confuse with total stranger" .)