Socially forbidden (5)
I believe the answer is:
taboo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">socially forbidden</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for taboo that I've seen before include "Strictly forbidden" , "Ritually forbidden" , "Socially prohibited" , "ruled out" , "(Irrational) prohibition" .)