The ornamental design for a feltedcover for a jar candle, as shown and described.
FIG. 1 is a front perspective view a felted cover for a jar candle showing my new design, the jar candle being shown herein and throughout in dashed lines and thus forming no part of the claimed design;
FIG. 2 is a side elevational view thereof, all additional side elevational views thereof being identical hereto; and,