There are two ways to do this (it may not be exact what you want but...):
Select the objects you want to render / open the Advanced render settings palette and under Render settings / Procedure you can select Selected. Now only the objects you've selected will be rendered.
Another method is to save the view you want to render:
Zoom in on the part of the drawing you want to render. Go to the Dashboard / 3D Navigate / click on Unsaved current view / at the bottom, click on New View... and save your view. (You can also click on the New Camera-icon, but then you have to set more settings). That will be easier to go back to this view in the future. In fact you've just created a Camera (camera's can be displayed by clicking on the Display Camera-icon in the 3D Navigate Control panel). And after that, click render. (Advanced render settings palette and under Render settings / Procedure you can select View.)