Pretty nice, tough Saturday puzzle. Lots of deceptive clues, like 7A: Main means of defense? (SQUIDINK). Early on I thought of the "Bounding Main," but I kept trying to come up with human means of defense at sea. Once QUINCE (8D: It might be in a jam) fell in, it really couldn't have been anything else. Didn't completely love (or, possibly, understand) 16A: Opted to duck (PUNTEDON), and LIMORIDE as a "18A: Prom amenity" didn't seem perfect. Not everyone going to the prom gets a limo (I guess I think of "amenities" as somehow free or included...), but I guess it's fine. In short, that NE corner was somewhat tough, even though we got DERBINGLE (11D: "White Christmas" singer, informally) with only a couple crosses. And we loved the Emerson quote.
Overall, the top went fairly quickly, but the bottom took some work. DRESSSUITS (47A: They're off on casual Fridays), for example, was first "sport coats" and then "dress codes" before we finally got it right. And we weren't familiar with MARINES being called 37D: Devil dogs, so that didn't help. We had just recently looked up the "Levant," so we got NEAREAST without difficulty, but the exact name of OTTERPOPs (52A: Frozen treat with Alexander the Grape as one of its flavors) had to be spelled out for us. Tried "Freez Pop" as a wild guess, but OzE didn't really make sense for "50D: A heavy metal band may have it." (ORE)
Coincidentally, the ATNO of Tungsten was a crucial part of the dénouement in a mystery we just watched the other day. Funny how things come together.
Enjoyed 44A: Dark green? (LUCRE), but we were hoping for more from 45A: Automotive plural selected in a 2011 promotion (PRII). I have no idea what that refers to (aside, of course, from the car itself). I am also unfamiliar with POI as a 25A: Pounded side, but, well, sometimes it's nice to learn things from the grids.
Overall, a good challenge.