I heard a familiar word today on the radio that was being used in a way quite unfamiliar to me

It is a typical language scenario where a noun has (by a process of synecdoche) come to stand for a complete activity, and by a back-formation has then spawned a new noun to describe the er, participants in this social activity. If I tell you that, like Sherlock, it's a case of the dog that did not bark, can you guess the term?

I believe it is a UKism, but please share if any of you know otherwise…!