French painter of peasants in grass (6)
I believe the answer is:
millet
'grass' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for millet that I've seen before include "Food grain" , "sort of grass" , "Type of cereal" , "Food-grain" , "Seed from cereal grasses - French painter, d.1875" .)