。
The children chased after the circus parade.
Literal
Children-[plural-たち] [subject-が] circus [attributive-の] procession [object-を] chased-after.
A simple narrative sentence. 追いかける ('to chase, to pursue') is a compound verb 追う ('follow, chase') + 掛ける ('cast, apply to') — the ~掛ける suffix here adds an 'actively directed toward' nuance. 行列 ('procession, parade, line') is used for parades, queues, and processions. サーカス is a loanword.