You are asking Articles Anywhere to show the custom field 'teaser' attached to the articles. Of all articles that are in that current category.
Articles Anywhere does not offer a way to show the value of custom fields attached to the category (not the article).
That would show the category name of all articles that are in that current category.
So if that category has 50 articles, you would see the category name 50 times.
To show data connected to the current article, simply do:
Unfortunately I am not available for custom work, projects or new extensions.
I have my hands full on getting the current extensions ready for Joomla 4.
What you could do is write (or search for) a piece of (Joomla) PHP code that collects the data you need from the database (based on the current cat ID), and output that.
You could use Sourcerer to place that code in your article.
Or use ReReplacer to be able to use a placeholder tag in your article, which can then replaced with PHP code.