The ornamental design for the clip for a window covering, as shown and described.
FIG. 1 is a front view of the clip for a window covering;
FIG. 2 is a rear view of the clip for a window covering attached to a window covering with a second clip included to show the design in a position of use;
FIG. 3 is left side view of the clip for a window covering attached to a window covering. The right side view is an identical view of the left side view shown in FIG. 3;
FIG. 4 is a top view of the clip for a window covering and is illustrated without the headrail environment being illustrated in broken line;
FIG. 5 is a bottom view of the clip for a window covering attached to a window covering;
FIG. 6 is an enlarged rear view of the clip for a window covering of area 6 that is circumscribed by broken lines in FIG. 2;
FIG. 7 is a right side view of the clip for a window covering shown in FIG. 6;
FIG. 8 is a cross sectional view taken along line 8-8 shown in FIG. 6 of the clip for a window covering shown in FIG. 6; and,
FIG. 9 is a perspective view of the clip for a window covering shown in FIG. 6.
The headrail, front shade material and rear sheet material of the window covering shown in FIGS. 2, 3 and 5 drawn in broken lines and the broken lines circumscribing the details form no part of the claimed design.