The ornamental design for a portion of a housing, as shown and described.
FIG. 1 is a perspective view from below of a portion of a housing in accordance with my design;
FIG. 2 is an enlarged side elevation view of the portion of a housing in accordance with my design, the opposite side being a mirror image of that shown; and,
FIG. 3 is an enlarged bottom plan view of the portion of a housing in accordance with my design.
The broken lines showing environmental structure are for illustrative purposes and form no part of the claimed invention.