Pornography (4)
I believe the answer is:
smut
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pornography</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that pornography can be written as smut)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for smut that I've seen before include "Obscene filth" , "Indecent stuff" , "Obscene word(s)" , "Lewd material" , "porn?" .)