Principle behind yin and yang (3)
I believe the answer is:
tao
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">principle behind yin and yang</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tao that I've seen before include "true path" , "Element of Chinese philosophy" , "Chinese way to be followed" , "Source of existence (Chinese)" , "The way of Chinese philosophy" .)