have an/(one's) ear to the ground
To listen for any indication of what is happening or will happen. A: "I'm not sure what's going to happen with this merger, so I have an ear to the ground." B: "Please let me know if you hear anything." I know Kim has her ear to the ground in case word gets out about the promotion.
ear to the ground, have one's
Also, keep one's ear to the ground. Be or remain well informed; be on the watch for new trends and information. For example, She knew she'd succeed as a reporter if she kept her ear to the ground. This graphic expression probably alludes to listening for distant hoofbeats by putting one's ear close to the ground. [Late 1800s]