The ornamental design for a director-diffuser for a firehydrant, as shown and described.
FIG. 1 is an rear elevational view of a director-diffuser for a fire
hydrant showing my new design;
FIG. 2 is a reduced top, front, and side perspective view thereof;
FIG. 3 is a reduced top and front perspective view thereof; and
FIG. 4 is a further reduced front and side perspective view thereof, with
the broken-line depiction of a fire hydrant body being for illustrative
purposes only and forming no part of the claimed design.