You're listening to The English We Speak from BBC Learning English, and Neil has been using the phrase 'a walk in the park' to explain that a run in the park is easy, especially when compared to other activities, like running a full marathon, for example.
你正在收聽 BBC 學習英語的《我們說的英語》,Neil 一直在使用「a walk in the park」這個短語來解釋在公園裡跑步很容易,尤其是與其他活動相比,例如跑全馬。