Colours for duke getting approval (4)
I believe the answer is:
dyes
'colours' is the definition.
(dyeing is a kind of colouring)
'duke getting approval' is the wordplay.
'duke' becomes 'd' (abbreviation).
'getting' is a charade indicator (letters next to each other).
'approval' becomes 'yes' (I've seen this in another clue).
'd'+'yes'='DYES'
'for' is the link.
(Other definitions for dyes that I've seen before include "Many a pigment" , "Colours (fabric)" , "Stains" , "Colouring materials" , "Substances for staining or colouring" .)