How can I theme a single value from a multi-value theme?
It seems like there are properties in $content['field_hero_slideshow_header_text'] which determine how it's themed. Perhaps a '#theme'.

Can you try making a copy of the entire field with just the value you want?

$content['field_hero_slideshow_header_text_copy'] = $content['field_hero_slideshow_header_text'];

// Unset all multi values, they have integer keys.
foreach($content['field_hero_slideshow_header_text_copy'] as $k =&gt; $v) {
  if (is_int($k)) { unset($content['field_hero_slideshow_header_text_copy'][$k]; }
}

// Add just the one we want back in.
$content['field_hero_slideshow_header_text_copy'][0] = $content['field_hero_slideshow_header_text'][0];

// Output single field.
render($content['field_hero_slideshow_header_text_copy']);

// Do you need to remove the field from the original array?
unset(render($content['field_hero_slideshow_header_text'][0]);


Not the nicest way I know. You could try copying properties from the parent to the child and it might output correctly, though I don't think so because the theme function probably expects data in a parent > child format.