Not clean (5)
I believe the answer is:
dirty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not clean</span>' is the definition.<br/ ><span class="explanation-format__explanation">('dirty' is the opposite to 'clean')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for dirty that I've seen before include "Unclean or indecent" , "Unscrupulous" , "1971 film with Clint Eastwood" , "Salacious" , "Not clean" .)