Religiously American people (5)
I believe the answer is:
amish
'religiously' is the definition.
The definition and answer are not the same part of speech.
'american people' is the wordplay.
'american' becomes 'Am' (abbreviation in some contexts).
'people' becomes 'ish' (I can't explain this - if you can you should believe this answer much more).
'am'+'ish'='AMISH'
Can you help me to learn more?
(Other definitions for amish that I've seen before include "American follower of the Mennonite religion" , "Community that settled in America" , "Mennonite sect members" , "One 24 [IN-SECT]" , "Religious group" .)