// import the filter classes
import flash.filters.DropShadowFilter;

// create a movie clip called shapeClip
this.attachMovie("myClip", 1);

// create a filter
var dropShadow:DropShadowFilter = new DropShadowFilter(4, 45, 0x000000, 0.4, 10, 10, 2, 3);

// apply the filter
myClip.filters = [dropShadow];