And by "establishment", which of the following does it refer to?

"Establishment" is a technical term in religious circles, with the precise meaning of a state-supported church. Outlawing such state support would be a very popular policy among those constitutioneers who had seen the consequences of England's established church at that time, not to say the terrible conflicts that used to ensue every time someone disestablished one church and established a new one in its place.

Peter