clinics_functions.php

function filter_clinics_index( $query ) {
    if ( !is_admin() && $query->is_main_query() && is_post_type_archive( 'clinic' )){
		
        $meta_query = $query->get('meta_query');
        if( is_array($meta_query) ) {
	        $meta_query['order_clinic_clause'] = [
		        'key'     => 'order_clinic',
		        'compare' => 'EXISTS',
		        'type'    => 'NUMERIC'
	        ];
        } else {
	        $meta_query = [
		        'relation'            => 'AND',
		        'order_clinic_clause' => [
			        'key'     => 'order_clinic',
			        'compare' => 'EXISTS',
			        'type'    => 'NUMERIC'
		        ]
	        ];
        }
        
        $order_by = [
	        'order_clinic_clause' => 'meta_value_num rand',
	        'rand' => 'DESC'
        ];
        
		$query->set( 'orderby' , $order_by );
		$query->set( 'meta_key' , 'promotion_date_end' );
		$query->set( 'meta_query' , $meta_query );
		//$query->set( 'order', 'DESC' );
    }
}
add_action( 'pre_get_posts', 'filter_clinics_index', 1 );