< class  name="Resource" table="T_RESOURCE">
  	<id name="id" type="long" column="resource_id">
  		<generator  class ="sequence">
  			<param name="sequence">resource_id_seq</param>
  		</generator>
  	</id>
  		
	<bag name="listTags" table="T_RESOURCE_TAG" cascade="none">
  		<key column="resource_id" />
  		<many-to-many  class ="Tag" column="tag_id" />
  	</bag>  	
  </ class >

  < class  name="Tag" table="T_TAG">
  	<id name="id" type="long" column="tag_id">
  		<generator  class ="sequence">
  			<param name="sequence">tag_id_seq</param>
  		</generator>
  	</id>  	
  	
  	<bag name="listResources" inverse="true" table="T_RESOURCE_TAG" cascade="none">
  		<key column="tag_id" />
  		<many-to-many  class ="Resource" column="resource_id" />
  	</bag>  	
  </ class >

Tag tag = getTag(); //здесь допустим получаю реальный persistent объект

Session sess = HibernateUtil.getSession();
Transaction tx = sess.beginTransaction();

sess.delete(tag);

sess.flush();