Rock service provided (6)
I believe the answer is:
massif
'rock' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'service provided' is the wordplay.
'service' becomes 'mass' (church service).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'mass'+'if'='MASSIF'
Can you help me to learn more?
(Other definitions for massif that I've seen before include "huge piece of crust" , "Geological formation of an IMF ass" , "Mountainous block" , "mountain peak" , "large amount of rock" .)