Title: The Short Form
Theme: Familiar phrases in which one word is abbreviated. That abbreviation becomes a word helping to form a silly phrase that relates to the clue.
23A. “Belt it out, Adam!”? = First person sing (singular)
38A. “I forbid you from providing special access”? = Don’t give an in (inch)
42A. Your father’s blockheadedness = Pop density (population)
66A. Coin flip with a penny? = Turn of the cent (century)
92A. Emotional problem that’s surprisingly fitting? = Apt complex (apartment)
94A. Prepared some amazing Mediterranean fruit? = Cut quite a fig (figure)
112A. Do a bad job as a watchman? = Lookout for no one (number)
I filled in the upper right section of the puzzle almost immediately, including 38-Across. Once I had that, the theme became quite obvious. For some reason known only to my brain, I had the most difficulty completing 92-Across. I got “Apt” right away, but “complex” eluded me for quite a while. Overall, this was an easy and enjoyable puzzle.
A few answers in the “you learn something new every day” category:
21-Across: Border river between China and Russia. Answer: Amur.
87-Across: Title parrot in a 1998 film. Answer: Paulie.
74-Down: Math set with an unspecified number of elements. Answer: N Tuple.
88-Down: Flower that symbolizes immortality. Answer: Amaranth.