The theme answers are common expressions where the last word ends with an “s,” but the “s” is dropped.
23A. Disappointing “Whose with me?” response? = Show of hand
25A. Work to maintain a C average? = Hit the book
31A. Mention that you know a secret? = Spill the bean
51A. One who’s read an encyclopedia’s first volume? = Man of letter
58A. Podunk’s directory? = Yellow page
71A. Having finished just one month of a job? = Wet behind the ear
87A. What one with a small nest egg enjoys? = Golden year
109A. Occasional klutz? = Butterfinger
121A. Beginning magician’s arsenal? = Bag of trick
123A. Go on a brief youthful binge? = Sow ones oat
Some interesting answers:
20A. Like a land baron. Answer: Acred. A new vocabulary word for me. My dictionary says it’s a synonymn for landowner
78A. Star of the most watched TV episode ever. Answer: Alda (Alan). I thought at first it might be the “Who shot J.R.?” episode on “Dallas.” But none of that show’s stars has a name with four letters. Obviously, it’s the final episode of “MASH.”
102A. It no longer sells maize or mulberry. Answer: Crayola. It took filling in several letters before it dawned on me this wasn’t about food. I did read that Crayola has changed a number of its colors, but I haven’t seen a box of crayons in years, i.e., since J. was a kid.
56D. Seasick sea serpent of cartoons. Answer: Cecil. Not a cartoon I’m familiar with.
111D. Runic letter for “th.” Answer: Thorn. A total mystery to me since I know zilch about runic alphabets. Acc. to Wiki, they were used to write Germanic languages before the adoption of the Latin alphabet.