We claim the ornamental design for an transitional image for a portion of a display screen, as shown and described.
FIG. 1 is a front view of the first image of a transitional image for a portion of a display screen;
FIG. 2 is a front view of the second image thereof; and,
FIG. 3 is a front view of a third image thereof.
The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1–3. The process or period in which one image transitions to another forms no part of the claimed design. The broken line drawings of elements, indicia, and words within the claimed design, and the portion of a display screen in all views is for illustrative purpose only and forms no part of the claimed design.