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