Theme: Splitter - Start the answer with the first part of the target word and end the answer with the last part.
17. Source of valuable metal: GOLD MINE
25. Early record player: GRAMOPHONE
37. Beatles song used as wake-up music on the last Space Shuttle mission: GOOD DAY SUNSHINE. Paul McCartney - Good Day Sunshine(2:05) The Beatles version unavailable.
45. Revolving blade sharpener: GRIND STONE
58. Extinct since way back when ... and, in a way, what each set of circles represents: LONG GONE
Argumentative style here. And for the sake of argument, this seems like a C.C. puzzle. The split is GO-NE or G-ONE, alternating. The circles seem superfluous.
1. Baseball putout, often: TAG
4. Digital readouts, for short: LCDs. (liquid crystal display)
8. No more than: AT MOST
14. 401(k) kin: Abbr.: IRA. (individual retirement account)
15. Settled on a rail: ALIT. Hope it's a fence rail and not a train rail.
16. Abs exercise: CRUNCH
19. Holy __: brat: TERROR
20. Isaac's eldest: ESAU
21. Golden State wine region: NAPA. Devastated.
23. One World Trade Center topper: SPIRE
24. Sales team: REPS
27. Give it __: make an effort: A TRY
29. Work's opposite: PLAY
30. Fibber or Molly of old radio: MCGEE
32. Rationale: BASIS
34. Repair: FIX
40. Mariner's "Help!": SOS
41. Tear to pieces: RIPUP
42. Makes, as money: EARNS
43. "Buona __": Gino's "Good evening": SERA
44. Former trans-Atl. fliers: SSTs. (supersonic transport)
50. Thing to scratch: ITCH
53. Cut again, as grass: REMOW
54. Bring into the firm: HIRE
55. About 66.5 degrees, for the Arctic Circle: N LAT. (north latitude)
56. Musician Keys: ALICIA
60. Poland Spring competitor: DASANI. H²O
61. Words to Brutus: "ET TU?"
62. Dist. you can see: VIS. DISTance/VISibility, usually in miles. Important for pilots.
63. The "S" in GPS: SYSTEM. (Global Positioning System)
64. Pest-control brand: d-CON
65. Md. summer hrs.: EDT. (Eastern Daylight Time)
1. Striped big cat: TIGER
2. Got up: AROSE
3. Islands visited by Darwin: GALÁPAGOS
4. On the __: at large: LAM
5. Like Saran wrap: CLINGY
6. Bahraini money: DINAR
7. Assembly instructions start: STEP A
8. Put-on: ACT
9. Violates a "private property" sign: TRESPASSES
10. Brown played by Candice Bergen: MURPHY. (TV Series 1988–1998)
11. "Blame It __": 1984 film set in Brazil: ON RIO
12. Disdain: SCORN
13. Little pigs number: THREE
18. Looked for prints: DUSTED
22. Intensifies: AMPS UP. 11
26. Actress Lena: OLIN
28. 1967 Neil Diamond song title line preceding "Go to my head": "RED, RED, WINE"
30. British sports cars: MGs
31. Pigeon sound: COO
32. Less-traveled way: BYPATH
33. Sch. with a Phoenix campus: ASU. (Arizona State University) Most students are on the Tempe campus.
34. Grade school crush, often: FIRST LOVE
35. Quaint quarters: INN
36. Kisses, in romantic letters: X'es
38. Hoity-toity manners: AIRS
39. Detesting: HATING
43. Polar expedition vehicle: SNO-CAT
44. Taken care of: SEEN TO
45. Mortarboard tossers: GRADS
46. Race with batons: RELAY
47. "What'd __?": returning traveler's query: I MISS
48. Lubricated: OILED
49. Campus midshipmen's prog.: NROTC. (Naval Reserve Officers Training Corps)
51. Dog or coyote: CANID
52. Nuclear trial, briefly: H-TEST
57. "Ready, __, fire!": AIM
59. Staple or nail driver: GUN
Notes from C.C.:
Happy Birthday to dear CrossEyedDave & Blue Hen! Thank you for the endless joy you've brought to our life, Dave! Thank you for the tasty food hacks you've brought to our blog as well, Blue Hen!