The power through which the Tao is made manifest or is actualised. Or, the virtue or power inherent in a person or thing existing in harmony with the Tao
Te is often translated in many different ways by many different translators and often the word used by the same author will be translated differently according to context. So I’ll approach this in a round about way to give its sense.
If I have power over others to make them do what I think is right, I do not have Te. But if I have the power to lead them to do what is right without them necessarily being aware of my influence, then I have Te. If I perform virtuous acts from a choice to conform to a code, if my virtuous acts are part of the ritual I perform to align my life with an ideal, my virtue is not Te. But if my instinctive, spontaneous actions are a manifestation of the ideal then my virtue is Te. Brute force is almost never Te and ritualised acts of righteousness are almost never Te.
The essential factor of self motivated personal development is that no one deliberately chooses the worse, they choose the best, so when character is built by the individual wishing to be simply the best person they can be, rather than by the default of cultural norms and subject to outside forces, it will tend towards the better. That which I continually do will become a function of who I am; becoming my nature not my actions. By continually bringing myself in line with the Tao (in the sense of The Way I Should Go) I become part of the manifestation of the the Tao.
Now the important parameter here is perhaps the the idea of being the best person one can be. The emphasis should be on the “they” in “best person they can be.” There is an ideal you, not an ideal generic person. Let me open this up more. If I have an ideal image of what the perfect human is and try to conform to it, I will likely miss and more to the point, for what reason am I trying to conform? Who set this ideal? Instead, I shall try to be the best ‘me’ I can be. Also, instead of having some arbitrary goal image, I simply make choices each day that I believe are heading me in the right direction I am not moving towards being the best me, I am in fact being the best me at this moment. I am on a journey and it is alway the path that is more important than the goal. This way I can live in the moment, content. If I live in the future, focussed on a goal I have not yet achieved, I will be discontent. If I live in the past, focused on mistakes I cannot change (the past is fixed) I will be discontent. By bringing myself in line with the path (the Tao) that appears to me to be right in this moment I am demonstrating Te.
So, to control your opponent, not through brute force, but by techniques that are in line with the laws of physics, the mechanics of anatomy and nature of psychology is Tao Te Kung Fu. To train and learn skills that you can use instinctively, that are appropriate for your individual attributes in the context of the moment you need them is Tao Te Kung Fu.