The ornamental design for a gate for a playyard, as shown and described.
FIG. 1 is a front perspective view of a gate for a play yard.
FIG. 2 is a front view of a gate for a play yard.
FIG. 3 is a back view of a gate for a play yard.
FIG. 4 is a first side view of a gate for a play yard.
FIG. 5 is a second side view of a gate for a play yard.
FIG. 6 is a top view of a gate for a play yard; and,
FIG. 7 is a bottom view of a gate for a play yard.
The broken line showing of the play yard is included for the purpose of illustrating the unclaimed environment of the entirety of the play yard and forms no part of the claimed design.