Um, no. Firstly, George Clooney is a man, and men are never widows, they're widowers.
Secondly, George's first wife, fellow actor Talia Balsam — the daughter of actors Martin Balsam and Joyce Van Patten — is alive and well. They started dating in 1986, married in 1989, and divorced in 1993. George has since said that he wasn't really ready for marriage, and doesn't “feel like [he] gave Talia a fair shot.”
All's well that ends well, however. Talia married her second husband, Mad Men star John Slattery, in 1998, and their son Harry was born a year later. They're still married today.