Hm. This is where I got the all-important first glimmer of the theme: IVNE and “Environmental.” If you look at 66-Across, there’s another bread crumb: “Certain endurance athletes” are IRONMEN, which sits perfectly in the center of “EnvIRONMENtal,” something I had certainly never noticed before. Then, at 69-Down, which starts with the final N in IRONMEN … there is no clue, just a hyphen. Crossing letters to the rescue, once again! 69-Down reads NTAL, and if you start at the end of 66-Down, the E in IVNE, and read up, over and down, you get your complete answer: ENVIRONMENTAL.
It’s hard to say what the most important component to this three-part trick is, but I relied heavily on the longer Across entry when I knew what I was looking for. Here’s another example that confused me greatly before I’d sussed out the theme. 117-Across, “Lasagna cheese,” is RICOTTA; 117-Down, which is the overarching theme clue, is “Orange-colored fruit pastry.” Both are food items; later, though, I recognized APRICOT TART.
Each of these long terms forms a particular shape in the grid, a three-sided rectangle (missing a bottom). The puzzle’s title is helpful in recognizing this, although I did not immediately make the connection: “What’s Hanging?” refers to the two Down entries that begin and end the term; they dangle from either end of the longer Across entry. Then, the revealer at 105-Across makes that connection even clearer: Those shapes represent something. A “Piece of furniture with parts that fold down, as depicted seven times in this puzzle” is a DROP LEAF TABLE.
On top of that, literally, is an endearing work of grid art. It took me a minute to see it: The upside-down T whose crossbar is right above the letters L-E-A-F-T in DROP LEAF TABLE resembles the base of a table; then, nine rows above that is a five-square-long table top, with a three-square-long leaf hanging vertically on either side of it. It doesn’t run up and hit you on the head, but it’s a fine touch.
20A. I had trouble parsing “Lets handle” at first (since “Let” and “handle” can each be a verb or a noun). In retrospect, only one interpretation makes sense: “Lets handle” is the same as LEAVES TO. (I wonder if there are some Easter eggs in the fill, like this use of “leaves.”)