Someone refusing to accept old money (6)
I believe the answer is:
denier
This clue is a double definition.
'someone refusing to accept' is the first definition.
(a denier refuses to accept something as true)
'old money' is the second definition.
(I know that denier is a subclass of disused coin)
(Other definitions for denier that I've seen before include "measure of yarn's quality" , "Conspiracist probably" , "measure of fine quality" , "Units of weight in silks, nylon and other yarns" , "Unit of measurement for silk" .)