frontline

also front line (frŭntˈlīnˈ)

1. A front or boundary, especially one between military, political, or ideological positions.
2. Basketball See frontcourt.
3. Football The linemen of a team.
4. Sports The players who play farthest forward, as in volleyball.

1. Located or used at a military front.
2. Of or relating to the most advanced or important position or activity in a field or undertaking: “leaders of the six black ‘front-line states’ bordering South Africa” (Boston Globe).
3. Sports
   a. Of or relating to the frontline.
   b. Being a member of the regular team; first-string: a team in need of a frontline catcher.