Belief in God is within Democrat (5)
I believe the answer is:
deism
'belief in god' is the definition.
(deism is belief in a god or gods)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for deism that I've seen before include "Belief in the existence of God" , "Belief in a god from reason not revelation" , "Belief in a creator" , "Belief in a supreme being who does not intervene in the universe" .)