18. *Steam: WATER VAPOR.
24. *Western capital: SALEM, OREGON.
40. *Systematic rumor spreading: WHISPER CAMPAIGN.
52. *Wite-Out alternative: LIQUID PAPER.
61. Hikers' starting points ... or what the ends of the answers to starred clues can be?: TRAIL HEADS.
The word TRAIL can follow the last word of each theme answer: VAPOR TRAIL, OREGON TRAIL, CAMPAIGN TRAIL, and PAPER TRAIL.
Across:
1. A third of XXX, maybe?: TAC. One third of the phrase tic, tac, toe.
4. Rorschach image: BLOT. See the original images here.
8. Make oneself decent, so to speak: DRESS.
13. "That's rough": ALAS. One of those words we mostly see in books and crosswords.
15. Clothing store website category: MEN'S.
16. Spunk: MOXIE. Mr. Grant hates spunk.
17. Colombian coin: PESO.
20. One in a Hollywood crowd: EXTRA.
22. Yoko who voiced a self-named character in 2018's "Isle of Dogs": ONO.
23. Sedate, say: DRUG. Verb, not adjective.
28. PC file suffix: EXE. An executable file for Windows.
29. Skip over: ELIDE. Another word not heard very often. A second definition is to join together or merge.
30. Come clean, with "up": FESS.
32. __ buco: OSSO. Means "hollow bone." Traditionally made with veal but can also be made with beef.
34. Paul who founded a pet food company: IAMS. Perps - had no idea.
37. Utterly lost: AT SEA.
43. "Buffalo Stance" singer Cherry: NENEH. Had not heard of artist or this song, released in 1988.
44. Fail to enunciate: SLUR.
45. Love of money, to all evil?: ROOT. Good to see this correctly, as it's so often stated that money is root of all evil, rather than the love of money.
46. Faltering step: TRIP.
48. Condescend: DEIGN.
50. "So pretty!": OOH.
57. Made fun of: APED. I guess so.
59. Zero-__ game: SUM.
60. Hyundai sedan no longer sold in the U.S.: AZERA. Discontinued in 2018.
65. Work on text, maybe: EDIT.
66. They're rarely worth splitting: HAIRS. True enough.
67. Blue prints, e.g.?: SMUT. Haha. An informal definition of blue is pornographic or profane.
68. Do a fall chore: RAKE.
69. Tear up: SHRED.
70. With everything in its place: TIDY.
71. Young guy: LAD.
Down:
1. Records, old-style: TAPES. Verb.
2. Siri counterpart: ALEXA. Alexa vs. Google vs. Siri.
3. Daydreams: CASTLES IN THE AIR.
4. Munich-based automaker: BMW.
5. Bucolic setting: LEA.
6. En pointe: ON TOE. Ballet.
7. Taiwanese golfer Yani __, youngest to win five majors: TSENG.
8. It's known for lines, briefly: DMV. Department of Motor Vehicles. True story.
9. Fork locale: ROAD. The proverbial fork in the road.
10. Steel guitar device: EXPRESSION PEDAL.
11. Dakota tribe: SIOUX. The Sioux Name and Dialects.
12. Suit material: SERGE.
14. Postgame griper: SORE LOSER.
19. It may be pitched: ROOF.
21. ProvenÁal pal: AMI.
25. Dog in the comics: ODIE.
26. Raises: REARS.
27. Half-moon tide: NEAP.
31. Telescope toter: STAR GAZER. My favorite astrophysicist. Love the nod to Carl Sagan's pale blue dot at 2:18.
32. Come clean, with "up": OWN.
33. __-crab soup: SHE. Made with lump crabmeat and crab roe.
35. Commonly injured ligament for NFLers: MCL. A sprain or tear to the medial collateral ligament - which is a band of tissue on the inside of the knee that connects the thigh bone to the lower leg. The MCL keeps the knee from bending inward.
36. Riyadh native: SAUDI.
38. Freudian focus: EGO. Sigmund Freud's Id, Ego, and Superego.
39. Carpenter __: ANT.
41. Singer Collins: PHIL.
42. TV's talking horse: MR. ED.
47. "Don't be silly!": PISH.
49. Brewpub initials: IPA. India Pale Ale. 11 Questions about IPA You're Too Embarrassed to Ask, Answered.
50. They're taken on stands: OATHS.
51. Daytime TV mogul: OPRAH.
53. Knight adventure: QUEST.
54. MSG flavor: UMAMI.
55. "Get Out" actress Alexander: ERIKA. Greta in A Nightmare on Elm Street 5.
56. Like books on goodreads.com: RATED. Meet Your Next Favorite Book.
58. Very serious indeed: DIRE.
62. Drug whose effects are similar to psilocybin: LSD. Where I Stand on Magic Mushrooms by Michael Pollan.
63. July 4th letdown: DUD.
64. Pigs' digs: STY.
