keep an ear to the ground意思是“保持高度警觉，对可能即将发生的事情保持警觉”或者“注意新闻、舆论动向”。

【例句】
Reporters keep an ear to the ground so as to know as soon as possible what will happen.
记者们注意舆论的动向，以便尽早知道将要发生的事情。

In this fast-changing world, journalists need to keep an ear to the ground.
在瞬息万变的世界里，记者需要注意舆论动向。