If you want a gradient to transparent it is not possible in AS. It is possible to have "halo only" or "shaded only", that could be similar in some aspects.
You could possibly draw your transparent object with gradient in Photoshop, save as a .png and import it into AS. The .png will maintain it's transparency in AS.
Only problem then is that if you zoom in, it'll pixallatte, and if you make it big enough to handle zooms, the Flash export will hate it. Guess it depends on what you're doing.
Yeah...
The problem gets hard if you want to work with a flashlite that distorts as long as it iluminates the ambient.
Not can do with AS and neither with PNG.