Sorry for the delay here, Kathrine – it seems like this topic feel through the cracks.
The basic principle described in the other post is still accurate, though: you should override the email template (event-tickets/src/views/tickets/email.php) by placing a copy within your theme directory (ie, themes/YOUR-THEME/tribe-events/tickets/email.php).
That copy should include code like this in a suitable location (where exactly depends on where you want to see the description, but it does need to be positioned after the line reading “foreach ( $tickets as $ticket ) {“):
echo get_the_excerpt( $ticket['product_id'] );
Does that help here?