snip

$tax_query = array(
	'relation' => 'AND',
	array(
		'taxonomy'         => 'category',
		'terms'            => '6',
		'field'            => 'term_id',
	),
	array(
		'taxonomy'         => 'post_format',
		'terms'            => 'video',
		'field'            => 'name',
	),
);