The ornamental design for a portion of a footwear upper, as shown and described.
FIG. 1 is a front perspective view of a portion of a footwear upper showing my new design;
FIG. 2 is a side elevational view thereof;
FIG. 3 is an opposite side elevational view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines immediately adjacent to the shaded areas represent the boundaries of the claimed design. None of the broken lines form part of the claimed design.