A podcast is just a blog with RSS/Atom feeds containing media enclosures. Once you've made a blog, ikiwiki gives you two ways to turn it into a podcast.
Put a media file where you'd put a blog post, and your
directive will include it as a media-only post.
Put the media file where
[[!inline ]] won't directly include it.
Write a blog post with
and your show notes.
See also migrating podcast to ikiwiki.