CLAIM The ornamental design for a user interface for a portion of a display screen, as shown and described.
Description:
The enclosed FIGURE is a front view of a user interface for a portion of a display screen showing the new design.
The broken line showing the display screen is for illustrative purposes only and forms no part of the claimed design. The shading below each of the rectangles represents a faded reflective shadow of a lower portion of its corresponding rectangle.