Realistically, isn't it a known presence on radar? It's static - you can't just ignore signals from that area in space?
Yes, and more...
You can use different antenna designs for a more directional radar beam. Or tilt the beam upwards to steer it around obstacles.
You can also build a moving-target detector by looking at doppler shift to filter out objects that are moving too slowly: https://en.wikipedia.org/wiki/Moving_target_indication
The enemy could be hiding precisely at the windmills /s
Yes, and more...
You can use different antenna designs for a more directional radar beam. Or tilt the beam upwards to steer it around obstacles.
You can also build a moving-target detector by looking at doppler shift to filter out objects that are moving too slowly: https://en.wikipedia.org/wiki/Moving_target_indication