gistfile1.js

initializer : function() {
    var client = this.get('client'), list;

    this.list = list = new ClientList({ client : client });

    // If this view has a different client, set the list client.
    // Inside of your ClientList, you probably want a bit of code that says
    // after the clientChange there, load myself... like:
    // this.after('clientChange', this.load, this);
    this.on('clientChange', function () { list.set('client', e.newVal); });

    // Then, when the ClientList is loaded, it will call render.
    list.after('reset', this.render, this);

    list.load(); // Initial loading
}

render : function() {
   // Typical rendering, and now you can be sure that the ClientList is loaded
   // (Unless something else is calling `render`)
}