the_excerpt_rss()

function the_excerpt_rss() {
	$output = get_the_excerpt();
	/**
	 * Filters the post excerpt for a feed.
	 *
	 * @since WP-1.2.0
	 *
	 * @param string $output The current post excerpt.
	 */
	echo apply_filters( 'the_excerpt_rss', $output );
}