Steps to reproduce the issue

Feature request
It is good to have at least the first few dozen characters of the tag descriptions shown in the admin tags list so you can see which tags are missing one or might need updating.
You can't quite achieve this with a template override of /administrator/components/com_tags/views/tags/tmpl/default.php because the description is not included in the model.
Thus a simple addition is needed to /administrator/components/com_tags/models/tags.php
in protected function getListQuery() somewhere around line 140 amend

	$this->getState(
		'list.select',
		'a.id, a.title, a.alias, a.note, a.published, a.access' .
			', a.checked_out, a.checked_out_time, a.created_user_id' .
			', a.path, a.parent_id, a.level, a.lft, a.rgt' .
			', a.language, a.description'
	)

adding , a.description to the select

Expected result

A template override can add a column for description using $item->description; and implement any length limitation and display stuff required.

Actual result

It throws errors (quite correctly) if you try to access $item->description;

System information (as much as possible)

j 3.9
macosx10.13.6 serving through MAMP
chrome browser

Additional comments

Actually if doing this you might as well implement the column in the view default.php
Personally I either restrict the length displayed to 100 chars and strip tags, or if I have a very long description I will break it into two parts with an <hr> (would be better as a [readmore] but by default the readmore button is only available in article editing) and only display the text up to the <hr> in list views (front and back ends) and use the full description when displaying the tag on its own.
Thus in /administrator/components/com_tags/views/tags/tmpl/default.php I have inserted a <th>...</th> in the relevant place and use

<td class="hidden-phone"><span class="small">
	<?php $text = $item->description;
          $brkpos = strpos($text,'<hr />');
          if ($brkpos) {
              $text = substr($text,0, $brkpos);
              echo strip_tags($text).' [more]';
          } else {
              echo JHtml::_('string.truncate', strip_tags($text), 100); //100 is my choice - could be a param
          }
      ?>
</span></td>

to display the description preview.
In the front end I don't strip the tags, but that's another story.