To find new supplier is expedient (8)
I believe the answer is:
resource
I believe this clue is a double definition.
'to find new supplier' is the first definition.
(re-source can mean to find a new source or supply)
'expedient' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for resource that I've seen before include "Available reserve to draw on" , "Anything that's there to assist when needed" , "Expedient - supply for use" , "Something that provides help when needed" , "Source of help" .)