We claim the ornamental design for a drum for washing machine, as shown and described.
FIG. 1 is a front/right-side/top perspective view of a drum for washing machine showing our new design;
FIG. 2 is a front-side elevational view thereof;
FIG. 3 is a rear-side elevational view thereof;
FIG. 4 is a left-side elevational view thereof;
FIG. 5 is a right-side elevational view thereof;
FIG. 6 is a top-side elevational view thereof;
FIG. 7 is a bottom-side elevational view thereof; and,
FIG. 8 is an enlarged view of a portion thereof.
The broken line showing of details in FIGS. 1-8 is included for the purpose of showing environmental portions of the drum for washing machine and forms no part of the claimed design.