How To Delete Crucible scores ?
(STEAM + ALL DLC)
Welcome to the forum. 
Not sure that you can. Maybe deleting the character would get rid of them, but that’s all I can think of.
I did it by totally wiping up my save data (chars, shared stash, blueprints). I don’t know if there is a less extreme method.
The less extreme method would be to delete or rename the file “leaderboard.brd” in your save game folder.