How to remove a persistent Kindle Reader tab in Safari on Mac?

I read library ebooks in Kindle and just recently there is a Kindle Reader tab in the first position in Safari on my Mac. There's no "x" to close it and when I quit Safari, then open in back up, all the other tabs are gone except this Kindle Reader as the first tab.

It's making me crazy because I don't want Jeff Bezos forcing his way into every aspect of my life.

Any ideas on how to disable or get rid of this would be appreciated.

Thanks! *See pic below, Kindle tab in first position.

[Re-Titled by Moderator]