Shade of difference? (6)
I believe the answer is:
nuance
I believe this clue is a double definition.
'shade' is the first definition.
('nuance' can be a synonym of 'shade')
'difference?' is the second definition.
(I have seen 'Subtle difference ' mean 'nuance' so perhaps 'difference' could also mean 'nuance')
'of' acts as a link.
(Other definitions for nuance that I've seen before include "Delicate shade of meaning" , "Subtle difference of meaning" , "Subtlety of meaning" , "Fine distinction" , "Subtle shade of difference" .)