Roman god of the underworld (3)
I believe the answer is:
dis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">roman god of the underworld</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 dis that I've seen before include "Treat without respect - god of the underworld" , "Speak disrespectfully to (colloq.)" , "Pluto's underworld" , "Greek underworld" , "The god Pluto" .)