Clownstrophobia (2009)

Patient X was found wandering near a carnival one night, she is trying to tell her nurse at the asylum that a killer clown has escaped and is heading home and her own baby was taken from her. As "Snuffles" arrives home, his sister Dr. Wethers is holding a group therapy session for delinquent teens who all fear clowns. It turns into a a real confrontation of their worst fears. Patient X is trying to get out and join the mayhem at any cost

Unfortunately the movie Clownstrophobia is not yet available on HBO Max.