UNION SELECT after LEFT JOIN and a JOIN statements in MySQL

I have four tables – reports_new, repuser_new, clients, users and the following query:

    SELECT DISTINCT rep.*     FROM `reports_new` rep     LEFT JOIN `repuser_new` ru     ON ru.`id_rep` = rep.`id`     JOIN `clients` c     ON c.`id` = rep.`id_client`     WHERE ru.`id_user` = '1' and rep.`name` LIKE 'urgent'     ORDER BY rep.date DESC 

EDIT: Without making any modifications prior to the WHERE clause, would it be possible to use UNION (or a better approach) after the LIKE statement in order to SELECT from a fourth table called users and ORDER the results BY rep.date DESC?