WordPress at a glance
filter is not described

rss_enclosure filter-hook . WP 2.2.0

Filters the RSS enclosure HTML link tag for the current post.

Usage

add_filter( 'rss_enclosure', 'filter_function_name_9206' );
function filter_function_name_9206( $html_link_tag ){
	// filter...

	return $html_link_tag;
}
$html_link_tag(string)
The HTML link tag with a URI and other attributes.

Where the hook is called

rss_enclosure()
rss_enclosure
wp-includes/feed.php 479
echo apply_filters( 'rss_enclosure', '<enclosure url="' . esc_url( trim( $enclosure[0] ) ) . '" length="' . absint( trim( $enclosure[1] ) ) . '" type="' . esc_attr( $type ) . '" />' . "\n" );

Where the hook is used (in WP core)

Does not used.