My infix means the head of a powerful clan.
My prefix has a machine enforcing its ban.
My suffix had an exceptional start to a dynasty.
You might say I'm a polite way to say something quite nasty.
The infix is also in the title of some restaurants. The prefix is scientific. The full word can be used in place of something sexual, but it has a much more common usage
The sushi restaurant in Scarborough inspired the clue for the infix, though you can find restaurants with the same name in West Hollywood and DeKalb, IL. The prefix is one mere element away from being essential to life.