I embedded a vimeo clip onto a website. Works fine.

I then added a second clip to my vimeo account and now the embed shows both videos. I only want one clip on that embed.

What did I do wrong now?

"now the embed shows both videos"

?

You mean when it plays out the viewer gets the option to view both?

Simple solution - got back into your account and delete the second video, or make it private, or pay fro a pro account giving you more control.

Fact is, vimeo has its own forum with folks that are much more clued up on Vimeo's nuances.