I think the current definition is pretty good. I would like to also note that leadership is not simply a singular quality or attribute, but rather it is a collection of different qualities and skills that are blended together and often have some overlap in between each component.
Furthermore, I would even propose that leadership includes the skill of discerning which qualities/values/skills are most needed for one's current situation, and which should be avoided due to the given state of affairs regarding the current situation.
For example, a skilled leader would be able to discern if a situation is edgy and rebellion is on the verge of breaking out. Given the high tensions, trying to assert a coercive decision-making process may result in a deterioration of the group and working environment. This is especially true if there is animosity focused primarily on the acting leader. Thus, the leader may respond by emphasizing the objectivity of utilizing a secret ballot vote to democratically choose whatever decision is at hand.
Obviously, there are times when the situation may be completely opposite, etc.
I will defer discussing values this week, because I feel I will be able to better talk about the complexities of that issue after we have read more articles on that topic.