The ornamental design for a golfclubhead for a putter, as shown and described.
FIG. 1 is a top perspective view of a golf club head for a putter showing our new design;
FIG. 2 is a rear view thereof;
FIG. 3 is a toe end view thereof;
FIG. 4 is a heel end view thereof; and,
FIG. 5 is a top view thereof.
The uneven broken line immediately adjacent to the shaded area represents an unclaimed boundary of the design. The unshaded rectangular region within the shaded region and the uneven broken line showing of the remainder of the golf club head for a putter are for illustrative purposes only and form no part of the claimed design.