[@_ck_ Participant 16 years, 3 months ago]

A little curiosity and trial and error will take you far when learning how to accomplish things.

If you look on front-page.php you’ll see it uses forum_description() so you can try

<?php forum_description(); ?> in your topic.php template.

If that doesn’t work, you may need to specify the $forum_id

<?php forum_description($forum_id); ?>