The ornamental design for "front portion of a visor," as shown and described.
FIG. 1 is a perspective view of "front portion of a visor" showing my new design
FIG. 2 is a front view of FIG. 1
FIG. 3 is a second embodiment of "front portion of a visor" showing my new design; and,
FIG. 4 is a front view of FIG. 3.
The broken line showing of the crown and the visor is for illustrative purposes only and forms no part of the claimed design, and the broken line shown in the solid line on the part of the crown represents stitching.