In the MMORPG Everquest, an assclown is someone who get's themselves killed due to a creature turing around during the last moments of a fight when the creature is using the ability enrage.
A male or female most of the time a female who enjoys ass sex. An ass clown enjoys learning about theater and lacks knowledge. Ass clowns tend to be reclusive.
An untalented schmuck who thinks his low effort at entertainment or "talent" will just simply work out for his benefit. You'll find that a lot of streamers, internet celebrities and youtubers will fit this definition.