This answer to What is this propellor-like object on top of the SpaceX Hopper? includes the following:
FCC filing: Space Exploration Technologies Corp. 0459-EX-CN-2020:
...d) List any natural formations of existing man-made structures (hills, trees, water tanks, towers, etc.) which, in the opinion of the applicant, would tend to shield the antenna from aircraft:
This radar will be attached to the top of a water tower and is masked between 164 to 290 degrees to avoid illuminating launch or test vehicles. Please note that a TFR will be in place when the radar is operating.
Question: What exactly does "TFR" stand for in this context? How does one put one in place when a radar is operating?