The ornamental design for a clockassembly, as shown and described.
FIG. 1 is a front elevation of a clock assembly showing my new design, the area in phantom being for illustrative purposes only and forming no portion of the claimed invention;
FIG. 2 is a right side elevation of the clock assembly;
FIG. 3 is a left side elevation of the clock assembly;
FIG. 4 is a top plan view of the clock assembly;
FIG. 5 is a bottom plan view of the clock assembly; and,
FIG. 6 is a top perspective view of the clock assembly.