The ornamental design for a clip-on wick sustainer, as shown and described.
FIG. 1 is a perspective view of a clip-on wick sustainer showing our new design, wherein the material shown dashed lines forms no part of the claimed design;
FIG. 2 is an enlarged scale perspective view of detail II-II in FIG. 1;
FIG. 3 is a top plan view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a side elevational view thereof; and,
FIG. 6 is a bottom plan view thereof.
The dash-dash-long dash lines of regular line weight immediately adjacent to shaded areas represent bounds of the claimed design. The dash-dash-long dash lines of bold line weight represent detail II-II in FIG. 1. All other broken lines in the drawing represent environmental subject matter that forms no part of the claimed design.