[Dr_Bra]

я так понял нужно учить гет и сет методы
вот правильный скрипт

package 
{
	import flash.display.*;
	import AdditionalClass;
 
	public class MainClass extends MovieClip
	{
		private var obj:MovieClip;
		private var star:AdditionalClass;
 
		public function MainClass():void
		{
			obj = obj_mc;
			star = obj.star_mc;
			star.mainClass = this;
		}
	}
}

package 
{
	import flash.display.*;
	import flash.events.Event;
	import flash.events.MouseEvent;
 
	public class AdditionalClass extends MovieClip
	{
		private var _mainClass:DisplayObjectContainer;
 
		public function AdditionalClass():void
		{
			this.addEventListener(Event.ADDED_TO_STAGE, init);
		}
 
		private function init(e:Event):void
		{
			this.addEventListener(Event.ENTER_FRAME, moveStar);
		}
 
		public function set mainClass(mainClass : DisplayObjectContainer):void
		{
			_mainClass = mainClass;
			_mainClass["obj_mc"].addEventListener(MouseEvent.CLICK, stopStar);
		}
 
		private function moveStar(e:Event):void
		{
			this.rotation +=  1;
		}
 
		private function stopStar(e:MouseEvent):void
		{
			this.removeEventListener(Event.ENTER_FRAME, moveStar);
		}
	}
}