has there ever been an nba finals clinching game that has resulted in a buzzer-beater to win that game?

Neither of Michael Jordan's shots to beat the Utah Jazz were buzzer-beaters. There was still time left for Utah to take a final shot, so MJ's shots didn't count as buzzer-beaters.
There hasn't been a buzzer beater to finish an NBA finals.

Several. The one I remember was on an MJ shot.

did you miss Jordan's career?

Bulls vs Jazz. MJ's jumper over Byran Russel.

Also, MJ vs Cavs - now, that was a real buzzer beater.