We claim the ornamental design for a clock display, as shown and described.
FIG. 1 is a top view of a clock display, shown located adjacent a competition area;
FIG. 2 is a front perspective view of the clock display, shown located adjacent the competition area of FIG. 1;
FIG. 3 is a top view of the clock display;
FIG. 4 is a bottom view of the clock display of FIG. 3;
FIG. 5 is a front view of the clock display of FIG. 3;
FIG. 6 is a rear view of the clock display of FIG. 3;
FIG. 7 is a left side view of the clock display of FIG. 3; and,
FIG. 8 is a right side view of the clock display of FIG. 3.
The broken lines in the drawings illustrate portions of the clock display that form no part of the claimed design. The broken lines showing a competition area illustrate environment and form no part of the claimed design.