There is no definitive meaning. The interpretation is up to anybody. The beauty of this phrase is that it can means so many different things ranging from innocent to down right diabolical. At one minute it could me that you are a clown performing clown stunts at a circus or a children's birthday party, another minute it could mean that you are committing illegal activities that are completely irrelevant to the subject of clowns. The choice is yours...
"I just finished creating my brand new Instagram account. Now what should I type into my bio that will express to others that I like to frequently have sex, shoot guns, scam people for there credit cards, and spread misinformation on the internet without actually saying it...? Ooh! I know!" *simply types: 'I be clownin'*