Essential to dump tin or the types the painters use (6)
I believe the answer is:
easels
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for easels that I've seen before include "Leases (anag)" , "Supports for paintings" , "Painters' stands" , "Artists' tripods" , "Supports in the studio" .)