Service provided in mountain region (6)
I believe the answer is:
massif
'mountain region' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'service provided' is the wordplay.
'service' becomes 'mass' (kind of church service).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'mass'+'if'='MASSIF'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for massif that I've seen before include "Geographical formation" , "Mountain centre" , "mountain peak" , "large amount of rock" , "Mountain heights in compact group" .)