The Tool clearance parameter allows you to specify an additional angle by which the tool sides should clear the material.
Tool with 5 degree side and end angles. The toolpath is grooving at 5 degrees.
Tool with 5 degree side and end angles, and 2 degree tool clearance. The toolpath is grooving at 3 degrees.
Tool sides keep touching the stock material
Tool sides are clear of the stock material by 2 degrees - the tool clearance angle