A clown — a comic performer, typically in a circus or theater. Figuratively can mean someone who acts silly to entertain or a tragicomic figure.
サーカスのピエロが観客を笑わせていた。
The circus clown was entertaining the audience.
彼は場を和ませるピエロのような存在だ。
He is like a clown who lightens the mood.
その映画ではピエロが不気味な役どころで登場した。
In that movie, a clown appears in a creepy role.