How to target the desired enemy champion with auto-attacks when the enemy team is stacked on the same spot?

I know about the "target champions only" keybind and using it but I wonder is there a way to lock into an enemy champion. I just had a baron fight with enemy team but all 5 of them were standing on each other so I hit the tank instead of my actual target few times. Is the only option trying to click on them or is there a setting to fix that?

note: I'm talking about melee auto-attacks not abilities.