Remove main navigation on one category

Question

I want to have a stand-alone category without any links to the rest of the shop.

Edit: Trying to add script to topmenu.phtml but not sure where to put it as using MegaMenu.

topmenu.phtml contents:

<div class="row">
<div class="span12">
    <nav>

    <ul class="nav nav-list hidden-desktop">
        <li class="nav-header"><a href="#level1" title="" data-toggle="collapse"><i class="icon-th"></i>&nbsp;&nbsp;
            <?php echo $this->__('MENU') ?> <i class="icon-down pull-right"></i> </a>
            <ul class="collapse in" id="level1">
                <?php echo $this->renderCategoriesMenuHtml(0,0,'','mobile')?>
            </ul>
        </li>
    </ul>




    <?php $class='class="simple"'; if(Mage::getStoreConfig('buyshoplayout/navigation/menutype')=='megamenu'){?>
    <div id="megamenu">
    <?php $class=''; }?>

        <ul id="nav" <?php echo $class?>>
            <?php if(Mage::getStoreConfig('buyshoplayout/navigation/home_button')){?>
            <li class="li-first-home"> <a href="<?php echo $this->getUrl('')?>"><i class="icon-home"></i></a> </li>
            <?php } ?>


            <?php if(Mage::getStoreConfig('buyshoplayout/navigation/menutype')=='simple'){?>
            <?php echo $this->renderCategoriesMenuHtml(0,0) ?>
            <?php } else { ?>
            <?php echo $this->renderCategoriesMenuHtml(0,0,'','megamenu') ?>
            <?php } ?>



            <?php if(Mage::getStoreConfig('buyshoplayout/navigation/custom_block')){?>

            <!--#1 DUPLICATE THIS SECTION IF YOU WANT MORE CUSTOM MENU ITEMS-->
            <li id="menu_custom_block"  class="level0 nav-2 level-top first parent">
               <?php echo Mage::getStoreConfig('buyshoplayout/navigation/custom_menu_url') ?>" class="level-top">
                    <span><?php echo Mage::getStoreConfig('buyshoplayout/navigation/custom_menu_title') ?></span> </a>

                <ul class="level0">
                    <li>
                        <div class="menu_custom_block">
                            <?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('buyshop_header_topmenu_custom_block')->toHtml()?>
                        </div>
                    </li>
                </ul>
            </li>
            <!--end #1-->

Answer 1

Add below code to template/page/html/topmenu.phtml

<?php $currentCategory = Mage::registry('current_category');
if($currentCategory && $currentCategory->getData('entity_id') == 6) //change your category id 
    return false;
?>

Just above <?php $_menu = $this->getHtml('level-top') ?>