Morally pure (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">morally pure</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for chaste that I've seen before include "Unsullied" , "Morally pure" , "Continent" , "Undefiled" , "Pure and decent" .)
(Another definition for sinless that I've seen is " Virgin".)