Scaleform Actors are stored in a hierarchical structure. That is, the Actor you want to destroy can be found inside a parent container, specifically a ContainerComponent. The ContainerComponent class contains the remove_actor() method which will remove the Actor from the scene, deinitialize it (that is, remove it from playlists, stop associated actions, etc.) and flag it for eventual deallocation.
Containers concept:
http://help.autodesk.com/view/ScaleformStudio/ENU/?guid=__scaleform_studio_help_programming_guide_sc...
And the remove_actor() method:
http://help.autodesk.com/view/ScaleformStudio/ENU/?guid=__lua_ref_obj_scaleform_ContainerComponent_h...
If the documentation doesn't provide enough detail to implement a solution please let me know and I can see about putting together a code example.
