Prerogative (5)
I believe the answer is:
right
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">prerogative</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a prerogative is a legal right)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for right that I've seen before include "Spot-on" , "one side" , "Correct; proper" , "Authority - one hand" , "True - just claim" .)