add_filter( 'posts_where' , 'location_posts_where' )


    function location_posts_where( $where )
        {
            // $lat  and $ lng are latitude and longitude of the searched point
            global $wpdb;
            $where .= " AND $wpdb->posts.ID IN (SELECT post_id FROM lat_lng_post
                 WHERE
                 (6371 * acos( cos( radians(" . $lat . ") )
                  * cos( radians( lat ) )
                  * cos( radians( lng )
                  - radians(" . $lng . ") )
                  + sin( radians(" . $lat . ") )
                  * sin( radians( lat ) ) ) ) <= 150
                    ORDER BY
                        ( 6371 * acos( cos( radians(" . $lat . ") )
                  * cos( radians( lat ) )
                  * cos( radians( lng )
                  - radians(" . $lng . ") )
                  + sin( radians(" . $lat . ") )
                  * sin( radians( lat ) ) ) ) ASC)";
                        return $where;
                    }

$args = array (
    'post_type'              => 'clinica',
    'orderby'                => 'none'

);

$args = array (
    'post_type' => 'clinica',
    'meta_key'  => 'distance_field_name',
    'orderby'   => 'meta_value_num',
    'order'     => 'DESC'
);