Painter's paste (5)
I believe the answer is:
gesso
'painter's paste' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gesso that I've seen before include "Artist's plaster" , "smeared on for starters by artists" , "Type of plaster" , "Could get you plastered" , "Plaster of Paris" .)