The region of religious writing (5)
I believe the answer is:
tract
'the region' is the definition.
(both can mean a large piece of land)
'religious writing' is the wordplay.
'religious' becomes 'tr' (I am not sure about this - if you are sure you should believe this answer much more).
'writing' becomes 'act' (act is a kind of writing).
'tr'+'act'='TRACT'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for tract that I've seen before include "Large area of land or small booklet" , "Extensive area of land" , "Large area; treatise" , "Stretch of space or time" , "Religious treatise" .)