您可以尝试以下操作：

/**
 * A sticky feed post from a given category
 *
 * @see http://wordpress.stackexchange.com/a/176706/26350
 */

add_filter( \'the_posts\', function( $posts )
{
    if( is_feed() 
        && $tmp = get_posts( array( \'category_name\' => \'feed\', \'posts_per_page\' => 1 ) ) 
    )
        $posts = array_merge( 
            $tmp, 
            wp_list_filter( $posts, array( \'ID\' => $tmp[0]->ID ), \'NOT\' ) 
        );

    return $posts;
} );