Clearing a REM object has one of two effects, depending on whether the object is associated with an image:
For example, you can define a region object and copy it to another area of the image. Then if you clear all objects, the original object (still associated with the image) merges into the image, but the copy (not associated with the image) is deleted.
You cannot do non-REM raster editing operations such as Touchup while REM objects remain in the image. The clear commands are useful for removing such objects after a REM editing session.