One unwilling to accept measure of fine quality (6)
I believe the answer is:
denier
I believe this clue is a double definition.
'one unwilling to accept' is the first definition.
(I've seen this before)
'measure of fine quality' is the second definition.
(I've seen this before)
(Other definitions for denier that I've seen before include "Measure of the fineness of silk or nylon" , "One who repudiates" , "measure of fine quality" , "A measure of material" , "Unit of weight for fine material, silk or nylon" .)