Governing (6)
I believe the answer is:
ruling
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">governing</span>' is the definition.<br/ ><span class="explanation-format__explanation">('rule' can be a synonym of 'govern')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ruling that I've seen before include "Decision as of judge" , "Drawing a fine line" , "Judgement" , "Court decision" , "Judge's decision" .)