Hi,
the feed content is created based on views/wpfc-podcast-feed.php file of SM plugin.
You can overwrite it by copying this file to your theme directory and modifying following line:
<itunes:subtitle><?php echo esc_html( $series ); ?></itunes:subtitle>
to
<itunes:subtitle></itunes:subtitle>
This will keep subtitle empty, but of course you can put there any php code to generate/extract subtitle from anywhere you want.
Hopefully this will help.
Have a nice day
Standa
P.S. I am just an user, not SM developer, so take is as non-official advice. But I have tried it on our church website and it worked. I tested it with version 2.13.1 of the plugin.
