You want the descent line from one ancestor to one of his/her descendants, right? With no side lines developed, right? 

1. Select the ancestor. 
2. Click Outline. After the report is shown, tailor it thus: 
3. Click Contents/Individuals to Include. You will see that you can display all descendants, or only those from the selected ancestor to a particular descendant.  
4. Click Direct Descendants from ... and Change Secondary individual. You will be presented with an index of all his descendants. Find and select your secondary person. Click OK.

Now you have the option of showing spouses of the direct descendants, or not. Click Contents/Options to select.

Once you have the ODT displayed, export it by: Click File/Copy, Export Individuals in Outline and follow further instructions.

You will have a choice of exporting as a FTW file or as a GEDCOM file. When you get to the dialog where you can name your output file, just below that space is the pulldown for type, which shows the allowable output types.

Click OK. Let the people say "amen".