The ornamental design for an outsole for a shoe, as shown and described.
FIG. 1 is a bottom perspective view of an outsole for a shoe in accordance with my new design;
FIG. 2 is a bottom view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a front view thereof; and,
FIG. 7 is a rear view thereof.
The broken lines shown in all of the figures are for environmental purposes and form no part of the claim. The broken lines shown on the face of the outsole in FIGS. 1 and 2 represent boundaries of the design with the lines themselves and the areas within them forming no part of the claimed design.