The barker at the fair entrance was enthusiastically inviting passersby to watch the circus show.

barker 是由动词 bark（大声喊叫）加上后缀 -er 构成的名词，指"大声吆喝招揽顾客的人"，通常指在集市、马戏团等场所门口大声宣传吸引观众的工作人员。