1) Adults-only 2) Arlington to Springfield dir 3) Atlantis to Xanadu dir 4) Cardinal 5) Compass direction 6) Dim bulbs have low ones 7) Final frame of a perfect game 8) Hard-core film rating 9) Lewdness letters 10) Madagascar roofing tool 11) Maker of the Sorento 12) Mars to Neptune dir 13) Part of a wriggly field Found on https://www.crosswordclues.com/clue/xxx
An identifier for sexually explicit material. Some model manufacturers cater to adult interests and packaging should indicate x-rated content. Found on http://www.encyclo.co.uk/local/20471