Short Answer: He ran out of ๐คก laughs!
Explanation: The clown was crying because he had used up all his jokes and couldn't make anyone laugh anymore. ๐คก A clown's job is to make people happy and when he couldn't do that, he felt really sad and shed some tears. But don't worry, once he comes up with some new hilarious jokes, those tears will turn into tears of joy! ๐