Hello @gis.analyst, this should be possible, but I am unsure we write to civil 3D as of current! We added 3D clipping support in FME Form 2022, which is nicely showcased in the Clip, Clip, Hooray webinar (~26min mark)! You would read the Candidate geometry using the Civil3D Reader, clip, and then write to Autocad DWG. Remember, when clipping, it is important for both datasets to share or be in the same coordinate system! Happy to help, Kailin.