Is it possible to apply a drop shadow effect to an object and then somehow make the object itself invisible while the drop shadow remains visible?
If I'm understanding your question correctly, then the effect that you are looking for can be achieved by creating a white object with a drop shadow and then setting the whole thing to MULTIPLY / DARKEN / OVERPRINT.
The result would look something like this:
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Or if the design is simple, make the object the same colour as the background e.g. white star / white background you would only see the shadow. You would need Chris's method for an export with transparency though. – Applefanboy Nov 28 '16 at 13:02
