It's the temp sensor for the heater box. The push button CCU gets input from 3 or 4 sensors.

If the antenna is stuck up, most likely is a worn antenna mast tail- it has ridges that wear down and the gears in the motor can't engage the tail to lower the mast. You replace the mast. Hopefully, it's not a dead antenna motor.

The clip you mention clips to the bottom center of the Becker radio. It's the connection to the anti-theft system.