stag = stag-do =stag night = bachelor party Sean is a guy's name. I live near the UK, but have never heard of a shop or club of this name.

It depends on the context. I've never heard of a shop or club with this name but then I don't know them all! Stag can be an animal - a male deer - but this is obviously unlikely. Stag can also be short for "stag do" - the party that men have before they get married. The male equivalent of a girls' hen do/night :) This is more likely!!