In the transloadit docs it mentions a parameter for the clipping path but I can't find any examples of how to actually use that.
See https://transloadit.com/docs/conversion-robots#image-manipulation-robots and look for the "clip" parameter.
If you set clip to true, then it will act as a toggle (automatically taking the first clipping). If you set it to a string it's the name for when there are multiple clippings in an image. Other operations in the step, then only apply to the selected clipping.