gistfile1.php

<div class="itens">
<?php
    $x=0;

    $query = new WP_Query( 'cat=3' );
    $total = $query->post_count;

    if ( $query->have_posts() ) {
        while ( $query->have_posts() ) {
            $query->the_post();
        
            if ( $x == 0 ) {
?>
        <div class="item">
            <ul>
<?  
            }
?>
                <li>
                  seu conteudo
                </li>
    <?php
            $x++; 
            $y++;   
    ?>        
    </ul>
<?php 
            if ($x > 9 || $y == $total ) { 
                $x=0; 
?>
            </ul>
        </div>
<? 
            }

        }//while
    }//if
?>
</div> <!--itens-->