Do they keep the artist well lubricated? (4)
I believe the answer is:
oils
'do they keep the artist' is the definition.
The definition suggests an adverb but the answer is not.
'well lubricated?' is the wordplay.
'well' becomes 'oil well' (oil well is a kind of well).
'lubricated?' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'oil'+'s'='OILS'
Can you help me to learn more?
(Other definitions for oils that I've seen before include "Soil, oddly, used by painters" , "Well-produced" , "landscapes, perhaps" , "Liquids for frying" , "Painting medium" .)