Tony,
Kind of like resin, which it may even be, although styrene cement works. Really brittle, and I don't know how to take advantage of the fact that they are clear.
Sometimes you know it helps to chop up the sprue in sections first. That avoids having multiple attachment points break while you are scutting one, breaking usually where you don't want it to.
Clip down to a stub and sand.
Glue with solvent.
Prime, as flash on a clear part can be hard to see.
Bill