$args = array(
        'meta_key' => 'pw_user_status',
        'meta_value' => 'approved',
    );

    $users = get_users( $args );

$args = array(
        'meta_query' => array(
            array(
                'key' => 'pw_user_status',
                'value' => 'approved' ,
            ),
        ),
        'orderby' => 'meta_value',
        'meta_key' => 'user_lastname',
        'order' => 'ASC'
    );
$users = get_users( $args );