Red line covers a page in centre of worship (6)
I believe the answer is:
chapel
'centre of worship' is the definition.
'red line covers a page' is the wordplay.
'red' becomes 'che' (Che Guevara the Marxist revolutionary).
'line' becomes 'l'.
'covers' means one lot of letters goes inside another.
'page' becomes 'p'.
'che'+'l'='chel'
'a'+'p'='ap'
'chel' enclosing 'ap' is 'CHAPEL'.
'in' acts as a link.
(Other definitions for chapel that I've seen before include "Private church" , "Perhaps part of cathedral" , "Place used for Christian worship - smaller than cathedral" , "Part of church with its own altar" , "Place of worship with an altar" .)