The ornamental design for a portion of a vehicleexterior, as shown and described.
FIG. 1 is a perspective view of a portion of a vehicle exterior showing our new design;
FIG. 2 is a side elevational view, the opposite side elevational view being a mirror image thereof; and,
FIG. 3 is a front elevational view thereof.
The heavy broken line depicts a boundary of the claimed design, and the broken line showings of the rectangles in the center step depict environmental subject matter and form no part of the claimed design.