The ornamental design for a portion of a footwearmidsole, as shown and described.
FIG. 1 is a perspective view of a portion of a footwear midsole showing our new design.
FIG. 2 is a right side elevational view thereof.
FIG. 3 is a left 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 showing the footwear upper, portions of the midsole and the outsole are for the purpose of illustrating environmental structure and form no part of the claimed design.