Make specific tag visible only to logged in users in front-end

Add the add_filter to your theme’s functions.php file

function myTags() {
$posttags = get_the_tags();
if ($posttags) {
  foreach($posttags as $tag) {
      if($tag->slug=='your specific tag slug'){
        if(is_user_logged_in() ) {
    echo '<a href="https://wordpress.stackexchange.com/questions/138827/.get_tag_link($tag->term_id)." >'.$tag->name . '</a> '; 
        }
    } else {
         echo '<a href="https://wordpress.stackexchange.com/questions/138827/.get_tag_link($tag->term_id).">'.$tag->name . '</a> '; 
    }
  }
}
}
add_filter('the_tags', 'myTags');