The ornamental design for a portion of an appliance, as shown and described.
FIG. 1 is a front perspective view of a portion of an appliance showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a cross-sectional view of FIG. 5.
The broken line showing of various regions, including the unshaded areas therein, is for illustrative purposes and forms no part of the claimed design.