WordPress at a glance
action is not described

load-importer-(importer) action-hook . WP 3.5.0

Fires before an importer screen is loaded.

The dynamic portion of the hook name, $importer, refers to the importer slug.

Usage

add_action( 'load-importer-(importer)', 'action_function_name_2338' );
function action_function_name_2338(){
	// action...
}

Where the hook is called

In file: /wp-admin/admin.php
load-importer-(importer)
wp-admin/admin.php 284
do_action( "load-importer-{$importer}" );

Where the hook is used (in WP core)

Does not used.