Once you reach the large room in the clock tower, the camera will zoom in on the Sand Troll with boxes. After defeating the enemies, the troll will keep throwing the exploding Sand Dogs. There are two weak walls on the left and the right. Go to the right one first to find a weak wall. Stand by it and look at the troll. When you see the troll throw those dogs, get out of the way. Look in the hole and you will see a water fountain. If you are running low on health and want to save a game, go right first. Do the same exploding tactic with the troll.