African country set up to accommodate second religion (5)
I believe the answer is:
islam
'religion' is the definition.
(Islam is a religion)
'african country set up to accommodate second' is the wordplay.
'african country' becomes 'mali' (country in Africa).
'set up' is a reversal indicator (in a down clue, letters go up).
'to accommodate' is an insertion indicator.
'second' becomes 's' (common abbreviation).
'mali' back-to-front is 'ilam'.
'ilam' placed around 's' is 'ISLAM'.
(Other definitions for islam that I've seen before include "organised religion" , "Belief" , "Religion based on teachings of Muhammad" , "Koran its scripture" , "Religious faith of Muslims" .)