On condition that one furnished supplies of (8)
I believe the answer is:
This could be a double definition.
'on condition that one' is the first definition.
'provided' can be an answer for 'on condition' (I've seen this in another clue). I'm not sure about the rest of the definition.
'furnished supplies of' is the second definition.
'provided' can be an answer for 'furnished' ('provide' can be a synonym of 'furnish'). I am not sure about the 'supplies of' bit.
Can you help me to learn more?
(Other definitions for provided that I've seen before include "Given" , "furnished" , "If - supplied" , "... on understanding that" , "in the event" .)