Conditional support for service range (6)
I believe the answer is:
massif
'range' is the definition.
(I've seen this before)
'conditional support for service' is the wordplay.
'conditional support' becomes 'if' (I can't explain this - if you can you should give a lot more credence to this answer).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'service' becomes 'mass' (religious service).
'if' after 'mass' is 'MASSIF'.
Can you help me to learn more?
(Other definitions for massif that I've seen before include "French mountain range" , "High points" , "Mountain heights in compact group" , "huge piece of crust" , "Geological formation of an IMF ass" .)