Unrighteous (6)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unrighteous</span>' is the definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sinful that I've seen before include "Morally wrong; wicked" , "Habitually wicked" , "very unpleasant" , "Fragrant climber" , "Wicked, unholy" .)