Painter's board (7)
I believe the answer is:
palette
'painter's board' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for palette that I've seen before include "Artist's colour-mixing board" , "Painter's utensil" , "Artists mix on this" , "Artist's range of colours" , "Range of colours - what artist mixes them on" .)