One clean, funny joke that is not a practical joke is just a single sentence: "A skeleton walks into a bar and says, 'Give me a shot -- and a mop.'" This joke comes from jokes.cc.com
Another option for a clean joke is this knock-knock joke from Reader's Digest: "Knock! Knock!"
"Needle little help gettin' in the door."
And for a longer joke that's still clean and funny, have you heard the one about the 600-story hotel from CleanJoke.com?
Tom, Dick and Harry went to a party. After the party they returned to their hotel. The hotel was
600 stories high. Unfortunately for them, the elevator was not working. They made a plan. For the first 200 stories, Tom would crack jokes. The second 200 stories, Dick would tell a happy story. And last, Harry would tell a sad story. They then started up the steps.
After two hours it was Harry's turn. He turned to the other two and said, "Okay, guys, here is my sad
story. I left the keys downstairs."