Render menu separately within admin
You can use one of these method.

Below method is used to print Main Menu in page.tpl.php file:

$main_menu = menu_navigation_links('main-menu');
$output = '&lt;div id="main-menu" class="navigation"&gt;';
$output .= theme('links__system_main_menu', array(
    'links' =&gt; $main_menu,
    'attributes' =&gt; array(
      'id' =&gt; 'main-menu-links',
      'class' =&gt; array('links', 'clearfix'),
    ),
    'heading' =&gt; array(
      'text' =&gt; t('Main menu'),
      'level' =&gt; 'h2',
      'class' =&gt; array('element-invisible'),
    ),
  ));
$output .= '&lt;/div&gt;';
print $output;


Or the example provided here:

$tree = menu_tree_all_data('main-menu');
menu_tree_add_active_path($tree);
print drupal_render(menu_tree_output($tree));