Add a clipping volume (box or sphere) in the Scene panel:
- Remove inside hides everything inside the volume, which is good for floaters or a passer-by.
- Keep inside hides everything outside, which is good for isolating a room or an object. Several "keep inside" volumes keep only the region where they overlap.
Clipping is non-destructive: the original upload is untouched and you can change or remove volumes at any time.