How can I remove certain HTML tags from the RSS feed?

One news aggregator wants to have RSS feed without any links into the <description> field. So I try to use this code in functions.php to remove <a href></a> tags, but it doesn’t work. What’s wrong? How can I remove the tags but keep intact all the text?

add_filter('the_content', 'my_custom_feed');
function my_custom_feed( $content ){
    global $post;

    if ( ! is_feed() )
        return $content;

    // Remove all shortcodes
    $content = strip_shortcodes( $post->post_content );
        $content = strip_tags( $content );

    // Remove all html tags, except these
    $my_allowed_tags = array(
        'p'      => array(),
        'strong' => array(),
        'em'     => array(),
        'img'    => array( 'src' => array(), 'width' => array(), 'height' => array() ),
    );
    $content = wp_kses( $content, $my_allowed_tags );

    // Balance tags
    $content = balanceTags( $content, true );

    return $content;
}