When I was learning to fly in 1967 in Merced, Calif., we had no control tower. We were taught that after engine start-up, we should pretend to call the tower for taxi clearance.
Another pilot trainee started his engine, then immediately started to taxi. The instructor stopped him and advised that he had forgotten to call for clearance.
The trainee thought for a second, opened the pilot air vent, and, over the roar of the engine, yelled, "Clear!"