Material that's just on the money (8)
I believe the answer is:
cashmere
'material' is the definition.
(cashmere is a kind of material)
'just on the money' is the wordplay.
'just' becomes 'mere' (I've seen this in other clues).
'on' says to put letters next to each other.
'the money' becomes 'cash' (I've seen this before).
'mere' put after 'cash' is 'CASHMERE'.
'that's' is the link.
(Other definitions for cashmere that I've seen before include "Fine soft wool for marchese" , "Fine wool for a schemer" , "fine cloth" , "'Fine, soft wool from a goat (8)'" , "Woolly stuff" .)