@ffm Yes, that could be the option since the head is indeed sticking out. But I'm scared to mess up the handlebar that way.
@|³|MA3K I don't have a torx at hand, but might try to get it. What exactly did you mean by torx head? A screwdriwer with torx xead, an "L" shaped key or a torx bit?
Cut/file a slot in it and use a screwdriver? (assuming I can see that properly and the bolt head is actually sticking out)