Short-term base artist used to produce painting (7)
I believe the answer is:
tempera
'painting' is the definition.
(I've seen this before)
'short-term base artist' is the wordplay.
'short-term' becomes 'temp' (as in a temp worker).
'base' becomes 'e' (I've seen this in other clues).
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'temp'+'e'+'ra'='TEMPERA'
'used to produce' is the link.
(Other definitions for tempera that I've seen before include "decorative style" , "Egg-yolk and water painting medium" , "Paint made using egg-yolk" , "vehicle" , "A paint and a painting technique" .)