Religion succeeded in revolutionary country (5)
I believe the answer is:
islam
'religion' is the definition.
(Islam is an example)
'succeeded in revolutionary country' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'in' means one lot of letters goes inside another.
'revolutionary' says the letters should be written in reverse.
'country' becomes 'mali' (Mali is an example**).
'mali' reversed gives 'ilam'.
's' put into 'ilam' is 'ISLAM'.
(Other definitions for islam that I've seen before include "Religion of the Koran" , "Religion based on teachings of Muhammad" , "Major world religion" , "Religion based on Muhammad's teachings" , "Adherents of a religion" .)