No clearance then No land.
That's easy to say, but what are you going to do next?
Land straight ahead provided the runway is clear. (We do this all the time at non-controlled airports).
Risk colliding with something on the ground.
Follow the missed approach procedure. Still no contact. Risk colliding with someone in the air?
There is no straight forward answer. Your experience and situational awareness (and gut feeling) on the day will dictate the most
prudent course of action.
The regulations do not provide for all scenarios!