I am stuck in the ice cave hideout with the moose behind the door. How..

I think where you are is in the caves where you need to fight off the moose who is charging you and whales the daylights of your character I should say. You need to hit him/her with the snow balls, just like anywhere else in game when you encounter the moose. I got there the first time and there were no snow balls, just bean cans and Windingos. No matter what I did I couldn't get him to melt away. I finally gave up and went out of the game without saving and started again, this time the snowballs were there and once my character hit him with enough, he melted away and the big round piece blocking the opening in the back of the cave moved away and I could get out.

I did that and the door didnt open am I doing something wrong ?

Yes, your doind it wrong, kill Frankenmoose(take a picture of him for the clubhouse case files!)and then magnify all the crystal stalegmites, (the pointy ice things surrounding the cave entrance.) As you will see, the crstals will change shape and become slightly smaller, watch them carefully, when they are finished kick them in the order they changed. There IS a slight limit for time, so be quick! If you do it wrong the sequence will paly again. When you kick them correctly they will be bigger like they originally were. Be fast and the entrance to the caves will opne. (By the way, make sure you kill all the Weendigos.)