field-under-slider-news3

$meta_query = array(
	'relation' => 'OR',
	array(
		'key'     => 'field-under-slider-news',
		'value'   => 'hide',
		'compare' => '=',
	),
	array(
		'key'     => 'field-under-slider-news',
		'compare' => 'NOT EXISTS',
	),
);