[WP] How to clear or modify cache

By default slider refreshes cache based on a value in option "Cache refresh time" (on slider "Settings" page), so slides are updated at a fixed interval in hours. To disable it set the option to 0.

If you wish slider to update when you save post, or during any other action, add such code to your theme functions.php (Instead of 123 there should be ID of your posts slider):

function rs_clear_cache() {
     delete_transient( 'new-rs-123' );
}
add_action( 'save_post', 'rs_clear_cache' );

Please note that "gallery" type of slider (that overrides [gallery] shortcode) has caching disabled.