From EF6.1, we have a way of specifying a clustered index on a property
public class Person { [Index(IsClustered = true, IsUnique = true)] public long U
Or this works too, say if you wanted to cluster by age...
modelBuilder .Entity() .Property(t => t.Age) .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute() { IsClustered = true}));