What does the phrase or expression "Missionary Teas" mean or come from?

Answer 1

They were basically just charity events; people in a church would get together to discuss and hear about the church's missionary activities abroad--obviously the goal was to raise money to support the mission.

Harper Lee describes one near the end of To Kill a Mockingbird.

Answer 2

It is the broth left over in the pot after the New Guinea tribesmen got done with the reverend....