You must enable port-mirroring on your switch. If you attempt to apply a policy that requires port-mirroring, the mirror action will be disabled until you enable the port-mirroring.
On Summit X450-G2, X460-G2, X670-G2 and X770 series switches, mirroring can be configured on the same port as egress ACLs. Mirroring can send packets to port x and you can install your rule at egress port x, and the rule should match your mirrored traffic.