Moral principle (5)
I believe the answer is:
ethic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">moral principle</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ethic that I've seen before include "Code of principles" , "System of rules of behaviour" , "Principles accepted by a social group" , "Set of moral values" , "System of principles" .)