The ornamental design for a miniature clocktower, as shown and described.
FIG. 1 is a front elevation view of a miniature clock tower showing my new design;
FIG. 2 is a rear elevation view;
FIG. 3 is a side elevation as seen from the left side of FIG. 1;
FIG. 4 is a side elevation as seen from the right side of FIG. 1;
FIG. 5 is a top plan view;
FIG. 6 is a bottom plan view; and,
FIG. 7 is a top, front and right side perspective view thereof.
The broken lines in FIG. 7 showing the face of the clock and the hour and minute hands are for illustrative purposes only and do not form part of the claimed design.