How to remove certain parts of an object?

Attached are the actual game scene & the game scene I am currently developing. As you can see, the obstacles are created by instantiating & randomly positioning them. Parts of the obstacles are hidden behind the top part & scene. I am using second camera to show the preview/timeline of the game(top right-hand side). As you can see, it is different from the actual game scene. The hidden obstacle parts are visible in the preview. Is it possible for me to remove them? Please help.

You can disable their renderer component and then use OnBecameVisible to enable their renderer again.