I’m not sure I know what you are asking for. Do you want to take a small clip out of a dvd and upload to Youtube?
If so, you can take a section out of the dvd with DVDShrink in ReAuthor mode using the Start / End Frames tool. The resulting output will be a small dvd video.
It depends on the size of the video whether this would be acceptable to upload. It is possible to convert to mp4 and make the resolution and total size of the video smaller.