The ornamental design for a portion of a whisk, as shown and described.
FIG. 1 is a front perspective view of a portion of a whisk showing my new design;
FIG. 2 is a side view thereof;
FIG. 3 is another side view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a front view thereof; and,
FIG. 7 is an enlarged cross-sectional view taken along the line 7—7 of FIG. 4.
The broken lines immediately adjacent to the shaded region form unclaimed boundaries of the design. The broken line showing of the inside of the whisk rod in FIG. 7 and the remainder of the whisk is for illustrative purposes only and forms no part of the claimed design.