Shockingly enough, it means that team is still in a raid. You can USE a team that's still in a raid (i.e. your team is wiped out, and waiting for the raid to finish), but you can't edit that party (because theoretically you could go back into the raid, use an Elixer, and revive them all).

Best case scenario: one of your guild members finished the raid. You'll get a popup saying to claim your rewards.
Worst case scenario: you'll have to wait for the daily reset to happen, at which point all the raids automatically finish.