Take a look into the com_content router, category blog view works like that,
shows a list of articles under domain.com/blog and the links are generated like
But it also allows something like this:
Therefore you have to change your link generating (JROUTE) in your component for the item, removing the item view. You can manually build the link to by parsing just the route to the list view, attaching the item alias to the url string.
This could be helpful too:
(I don't do that for my components I just redirect everything to the main view and then check the segments with an external router class.)