<$let previousCurrentTiddler=<<currentTiddler>> >
<ul>
  <$list filter="[tag[Meeting]!sort[at]]">
    <li>An item on <<previousCurrentTiddler>>: <$link to=<<currentTiddler>>/></li>
  </$list>
</ul>
</$let>

It turns out this is a sufficiently common pattern that there's an attribute you can add to the $list widget to make it easier, called variable. This attribute defaults to currentTiddler, but if you set it to something else, the current tiddler will be unmodified and that other variable will contain the current item being listed:

<ul>
  <$list filter="[tag[Meeting]!sort[at]]" variable="meeting">
    <li>An item on <<currentTiddler>>: <$link to=<<meeting>>/></li>
  </$list>
</ul>