Thank you for an entertaining cryptic; great first effort.
You have overlooked word length indicators in your clues. This made 13D impossible for me to solve without a reveal.
12D totally foxed me! Parse, please.
15A Definition of "obsess"?
8A Parse, please.
2D seems to make no sense at all!
The good news is, though some crossings are underchecked and some clues are stretching the "rules," it's a solvable puzzle with some fun stuff. I really liked 20A (though some might quibble that it needed to be "Long."), 13D, and 4D. I liked the idea of 16D, but I wasn't sure what "no longer fruity" was doing there. Ditto 14D: it seems like this is meant to be P(S)ALM, but if so, not sure what "Half of" and "about" are doing as positioned.
Two good suggestion I was given: (1) always substitute letters for words to make sure the cryptic grammar works as intended and (2) re-read the surface sentences to ask if they make sense. In the case of 10A, Make [A] out of [B] suggests an indirect anagram, and I don't understand the whole clue. Ditto 12A: if this is meant to be P(HAS)E, I don't see how to get "HAS" from "odd answer." (I might be misparsing!)
Most of this was indeed quite bad. Luckily there are plenty of sources out there to help you improve as a cryptic setter. Might I suggest "Palm Sunday's boring hymn" for 14D?