Code:
{author_sort}{series:| - |}
See:
http://manual.calibre-ebook.com/temp...ced-formatting for the gory details and HOWTO.
EDIT: myki -- didn't see your post until I posted. But there really is no need to jump the gun and assume only the first author is wanted.
Also, you might want to consider reducing your own template to:
Code:
{authors:sublist(0,1,&)}{series:| - |}
Or for that matter,
Code:
{authors:list_item(0,&)}{series:| - |}
works fine too.