The ornamental design for a rearcombinationlamp for an automobile, as shown and described.
FIG. 1 is a front side perspective view of a rear combination lamp for an automobile, showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof; and,
FIG. 4 is a top plan view thereof.
The broken lines shown in the drawings illustrate portions of the rear combination lamp for an automobile that are environmental structures and form no part of the claimed design.