Compound noun: Farmer.
Viljelijä by itself also means farmer. Maan is the genitive form of maa, meaning ”earth,” so it means ”farmer of the earth.”
Viljellä is a verb meaning ”to cultivate,” ”to farm,” or ”to till.” By adding the –jä ending it becomes an ”agent noun” describing one who performs the action.
Another related word is vilja, a noun meaning ”grain” or ”cereal.”