Include text in echoed hyperlink

Never just print the result of get_the_term_list() without additional checks. It might return an instance of WP_Error which is an object, not a string.

Save the result of get_the_term_list() in a variable and print the terms only if there are terms and not an error:

<?php
$stores = get_the_term_list( $post->ID, 'store', '', ', ' );

// We got something back, and it is not an error.
if ( ! empty( $stores ) and ! is_wp_error( $stores ) )
{
    echo "<p class="excerpt">
        <strong>Bekijk meer van extra1 $stores extra2</strong>
    </p>";
}
?>