Other forms: kept the wolf from the door; keeping the wolf from the door; keeps the wolf from the door
The idiom keep the wolf from the door means to earn just enough money to survive on, avoiding extreme poverty, but probably not having much left over for luxuries like fancy restaurant food or new clothes.
This expression dates from the 1500s. Wolves were often demonized as being savage, fearsome beasts that prey on people. While this is not the case, this view of wolves survives to this day in stories like "Little Red Riding Hood" and "The Three Little Pigs," in which the big, bad wolf is the villain. In keep the wolf from the door, the wolf primarily represents poverty or extreme hunger, but it could also represent a threatening financial force, like a greedy debt collector or a heartless landlord, who is literally knocking on someone's door to collect a debt.