There isn't quick way to clip surfaces by areas currently.
Perhaps introduce a new transformer which performs clipping surfaces by areas, or upgrade the Clipper transformer to accept surfaces as Clippee.
It would be ideal if solids could also be clipped by areas.
Yes, I was also looking for a 3DClipper or something recently!
An option to temporarily set a Z value for the area (in case it's 2D and doesn't intersect in Euclidean space) and to clip everything above or below the area would then be handy, I think.Similarly: I used this https://knowledge.safe.com/questions/36668/return-xy-coordinate-of-certain-z-value-along-poly.html?childToView=36739#answer-36739 to "clip" 3D lines "BY" surfaces.
So frustrating ... it is still the case in 2019
SurfaceClipper is here https://hub.safe.com/publishers/safe-sandbox/transformers/surfaceclipper
Surface clipper works, thanks to the contributer. Performance is not brilliant, mainly the speed running the deaggregator. This is compounded when you want to clip a surface against multiple groups of clippers. A group by or some kind of pass through is needed to ensure the deaggregation only happens once instead of using multiple surface clippers.