How do you get single-spaced line breaks?! Anyway:
1A: Great surface and [could spell] is a great anagrind.
5A: Wonderful use of a positional indicator for surface sense.
6A: [November to leave] is neatly cooked into this surface. Didn't realize until solving why you chose [take a side]. Good!
7A: Great anagram that adds to the surface sense.
1D: My second favorite clue. [Surrendering is] is so natural.
2D: My least favorite clue, though that's just comparative. I'm not sure I buy SUB for Subway. That's definitely something you can get at a Subway, but maybe usage has just changed here.
3D: My favorite. [Plumbing issue] is dastardly! Everything works for the surface. Amazing!
4D: A bit strained to make [flat] work in this surface sense, but nice cryptic play.
If you put two spaces on the end of a line before a single line break then you’ll get a regular break. Markup is a strange beast!
I think your ranking of the clues is more or less the same as how I see them. As for 2D, Chambers defines SUB (noun, informal) as “a subway”, among many other things. So a word for an underpass in general, rather than the chain (franchise?) specifically. It wasn’t a usage I was familiar with either, perhaps I shouldn’t have blindly put my faith in the Big Red Book!
Lovely solve! I was looking for an example puzzle to solve to show a friend how cryptics work and this was perfect! I noticed the schrodinger; that was a very cute touch. Love the definition on groove as well.
Nice work. I don't love the fill on 4D and would probably have chosen EYELETS or something by preference, but that's just me. 3D I bashed in without understanding the wordplay, but it seems fair, fun, and nicely tricky.
Thanks for the comment! Very fair point on the 4D fill. Originally I did have EYELETS in but was struggling to find an interesting way to clue it. I do agree that it would have yielded an overall better grid, so maybe I should have stuck with it.
5A: F[unk] + I’S + SURE
6A: U[-n]TIL + I + [dar]E to take S/Z (one side in ShowbiZ)
7A: SEATING*
2D: SUB< + KING
3D: CA(UTI + [w]O[rkman])N
4D: (S+REN[t]+EVE)<