Tower Local Controller reported a departing small general aviation aircraft reported smoke in the cockpit returned and landed on a runway before an air carrier could exit the runway.

Narrative

Aircraft X [requested priority handling]. I instructed them to tear drop back to the airport. Aircraft Y was in position on Runway XXL at the intersection where Aircraft X departed from. Aircraft X was tear dropping back but Aircraft Y did not exit the runway in time. Aircraft X was now on a downwind for XXL at approximately 400 ft. passed YL and said I need to land now I see that plane holding opposite direction I'll hold short of him. Aircraft Z was in position on Runway ZZR was told to exit at xx but didn't clear the runway edge before Aircraft X crossed the threshold for YL. Again Aircraft Y was told to exit the runway as soon as possible. Since Aircraft Y was unable to exit in due time; Aircraft X was not able to land on that runway safely; they had to land immediately on the runway they were crossing which was YL/ZZR. On the YL side. Aircraft Z was in position on ZZR. Aircraft X said they saw the Aircraft Z and would hold short of the aircraft but I still instructed Aircraft Z to exit the runway at xx. Aircraft Z exited at xx but not clear of the runway edge before Aircraft X crossed the threshold since they turned to land already inside the threshold. No recommendation can't stop an emergency smoke in the cock-pit.