Well, the theme’s no mystery, just like the title says, lots of wordplay involving tennis, i.e. common phrases that could easily be about tennis and literally mean what the clues say, but of course have more common meanings as expressions.
So here are 10 hints to the crossword’s non-theme answers:
1. (1-Across) Polite response to “thank you”: 3 words
2. (9-Across) Classic verse that begins, “Ah, broken is the golden bowl”: More commonly we think of a particular bird in association with this poem. Not the Maltese Falcon, but close.
3. (46-Down) Eliza Doolittle, for one: Yes, the flower girl cum aristocrat in My Fair Lady, but the answer is a very generic response to the clue, not specific to Eliza.
4. (90-Down) Franki Valli sang in it: No, he didn’t sing in the rain. Really, the “in” here is intended to mislead, though perfectly correct. He was “in the rain” or “in a subway” or “in” anything else like that. Perhaps you aren’t thinking highly enough of his singing?
5. (76-Down) Abbr. after a period: No, it isn’t et al. That comes before the period. Think internet.
6. (99-Down) Container on a counter: 2 words. Remember when you weren’t expected to use these when you got your morning java?
7. (51-Down) White Castle offerings: I know, you deny ever eating one of these, but they’re name tells you how easily they go down.
8. (76-Across) Source of the line “…they shall reap the whirlwind: Yes, it’s from the Bible, but you’re gonna have to be more specific.
9. (93-Down) Jefferson’s Vice President: And they say VP’s rarely become Presidents. Took this one (or at least his name sake) more than a century to do it!
10. (69-Down) As expected: 2 words. Think theatre.