WordPress: Wrap content output in a div

functions.php

<?php
add_action('loop_start', function() {
  // Only for archive
  if (is_archive()) {
    echo '<!--- Start loop wrap --><div class="wrap">';
  }
});
add_action('loop_end', function() {
  // Only for archive
  if (is_archive()) {
    echo '</div><!--- END loop wrap -->';
  }
});