Wonderful Tonight was written about Pattie Boyd, Eric's wife at the time. He wrote the song while he was waiting for her to get ready for a party (just as the song says).
No, actually Clapton himself said it's about the fact that he never knew his father, and the closest he ever got to looking in his father's eyes was when he looked in his son's eyes. And now his son...
If you wanna hang out you've got to take her out; cocaine. If you wanna get down, down on the ground; cocaine. She don't lie, she don't lie, she don't lie; cocaine. When your day is done and you...