Sounds like your bathtub is the far end of the drain, then the toilet, then main out of the house. There is a clog after the toilet headed out of the house. Because there is nowhere to have forced the clog in the toilet out it backed up to the bathtub. When you flush and get clear water it’s because there’s nowhere for the flushed water to go in either direction.as everyone else is saying snake that shit.

Make sure you let us know how it got resolved!