The clearance area type has a cylindrical shape and should enclose your drive surface geometry completely. So set a right radius, which gives you the diameter of the cylinder. The orientation can be the x, y or z axis. With default value the center of the cylinder is the line of the axis. Setting an offset through x, y and z moves the cylinder parallel to the axis.
Now the tool retracts to this cylinder radius and moves along the shell.
Here you can see a machining of a turbine blade. Only the sides of the blade should be machined, so the small radius surfaces are left out. Here the tool retracts to the clearance area cylinder. The cylinder is parallel to the x-axis.
As you can see the turbine blade center is not exactly through the x-axis. To move the cylinder you can set an offset to the x-axis so that the axis of the cylinder moves to the center of the turbine blade.
After setting the offset through the x-axis the cylinder moved down.