In which I take it on the chin

Okay. The answer is WOOZY ON THE GO

Perhaps an explanation is needed. In L. Frank Baum's Oz books, the Woozy (https://www.google.com/search?q=woozy%27s+tale+drawing+woozy+oz&udm=2) whose body is composed of square block parts. So when I saw this pattern of black squares in a crossword I thought "Oh, that looks like a woozy". See the two squares look like an elongated brick body and the the kitty corner square like a cube head. (I used to play with cigar boxes, holding them upside down and pretending the lids were the mouths of a square-headed Woozy). So I thought I'd make a gride where all the black squares were a bunch of little woozies marching across. But where to hide the letters? Well, I figured I'd put them nested between the two blocks-- on the woozy's chin.

The Woozy was introduced in the 7th book "The Patchwork Girl of Oz" and all the reference in the clues describe him or incidences in the Oz books.

And here are all the Oz references

8A- TikTik was a wind-up mechanical man who had springs for all activities including thought. Introduced in Ozma of Oz and had very few interactions with the Woozy.
11A- Eureka was Princess Dorothy's pet kitten who was inexplicably pink. Bungle was a glass cat with pink brains (you can see 'em work) and red stone heart. She was brought to life by the same Powder of Life that brought the Patchwork Girl to Life.
17A- A famous illustration https://cdn.shopify.com/s/files/1/0432/1981/files/WamegoPGWoozyHairPullCropped_480x480.jpg?v=1693252385 depicts the Woozy hugging a tree as Ojo and Scraps, the Patchwork Girl try to pull the three hairs from his tail. The three hairs where a require ingrediant in a potion that Ojo, a Munchkin boy, needed.
31A- The Patchwork Girl was made to be a servant and so was made with brains to by loyal and obedient and only minimally clever. Ojo thought this would be a poor lot in life so while no-one was looking he snuck in extra drops of various other fun loving traits.
35A- Cap'n Bill and Trot were a sailor and a young girl from a coastal town in Southern California. The ended up in Oz after their own series didn't sell that well. They had very little interaction with the Woozy.
38A- That was basically the first half of the book.
41A- Baum wanted to end the Oz series in the 6th book with Oz being shut off from the outside world by a barrier of invisibility. When he decided to bring it back in the 7th book (The Patchwork Girl) he explained he communicated via wireless radio.
1D- Oz is surrounded by the Deadly Dessert on which nothing can grow and any living thing will turn to dust if they touch it.
33D- The magic picture is used by Princess Ozma to, well, spy on anyone she wants at any time-- I always found that a little creepy.
50D-- The Woozy's favorite food is live honey-bees. His eyes flash fire when he is angry. (He also has what he thinks is an earth-shattering growl but is in reality a pathetic squeak.)