Theme: It's an ill wind that blows nobody any good - Not an ill wind in the bunch.
17A. "American Gothic" artist : GRANT WOOD. You might find an off-key (ill) WOODWIND, I suppose.
21A. Equitable transaction : EVEN TRADE. Winds that trade or tread in one uniform track. (Anglo Saxon, tredde-wind, a treading wind—i.e. wind of a specific “beat” or tread; tredan, to tread.) While a steady wind in one direction may be good for commercial maritime venture it was not the meaning of the TRADE WINDS.
38A. "Now!" : RIGHT THIS SECOND. A SECOND WIND is an exercise phenomenon that has also developed into a metaphor for finding the strength to go on after initial struggles.
55A. Award for seagoing heroes : NAVY CROSS. A CROSS WIND blows across one's direction of travel. Not so good for a sailing ship following the TRADES.
61A. Flying speed boosters ... or, literally, what the ends of 17-, 21-, 38- and 55-Across can have : TAILWINDS
Argyle here. C.C. has company today and I sure she'll tell us about him. Very nice puzzle to debut with. Full spanner and reveal at the bottom, the way it should be, right?
1. Ways to go: Abbr. : RDs. Roads, not routes.
4. Ltr. addenda : PSS. Is it P.P.S or P.S.S? Well, since addenda is the plural of addendum then this should be considered as the plural of POST SCRIPT, or PSs.
7. None too bright : DENSE. (or am I dense.)
12. Obama's birthplace : OAHU
14. Somewhat surprised greeting : "OH, HI!"
16. Nebraska city : OMAHA
19. Golf course halves : NINES. Front and back or out and in, on a link course.
20. Causing goose bumps : EERIE
23. Scolding sound : [TSK!]
24. Belted weapons : SIDE ARMS. Pistols or swords.
26. Camp beds : COTS
28. Poet __-tzu : LAO
29. Strong coffee : MUD
32. NCAA's __-12 conference : PAC. (The Pacific-12)
33. Italian sparkling wine : ASTI
36. One of two in a typical string octet : VIOLA
41. Beyond rotund : OBESE
42. Round in a pistol : AMMO. For your side arm.
43. Writer LeShan : EDA
44. Conan O'Brien's network : TBS. (Turner Broadcasting System)
45. Org. with Raiders and Vikings : NFL. (National Football League)
47. Folk singer Burl : IVES
49. Retired boxer with a perfect 24-0-0 record : LAILA ALI. Daughter of Muhammad Ali.
52. Serious hostilities : WAR
58. Say "cap'n," e.g. : ELIDE
60. Cheri of "SNL" : OTERI. Still around.
63. Shirk work : DOG IT
64. Easy thing to do : SNAP
65. Wrinkled tangelo : UGLI
66. In la-la land : SPACY
67. __ Arbor, Michigan : ANN
68. One of a D.C. 100 : SENator
1. Man of many words : ROGET. Roget's Thesaurus was created in 1805 but not released to the public until 1852.
2. Shows some backbone : DARES
3. Protective enclosures for divers : SHARK CAGES. 18 footer.
4. "Bang!" : "POW!"
5. Did a blacksmith's job : SHOED
6. Push rudely : SHOVE
7. "Keep still!" : "DON'T MOVE!"
8. Mideast dignitaries : EMIRs
9. Mom's mom's nickname : NANA
10. Place for a lawn mower : SHED
11. Alleviate : EASE
13. Prefix with lateral : UNI
15. High-mindedness : IDEALISM
18. Word after screen or scratch : TEST
22. Agency under FDR : NRA. (National Recovery Administration)
25. "The wolf __ the door" : IS AT
27. Folk legend Phil : OCHS
29. Sudden changes in disposition : MOOD SWINGS
30. Wrist-to-elbow bone : ULNA
31. Mom's guy : DAD
32. Mr. __: Dr Pepper rival : PIBB
34. Kitchen bulbs : SHALLOTS
35. Tiny Dickens boy : TIM. A Christmas Carol.
37. Java Freeze maker : ICEE
38. Poppycock : ROT
39. Stick-to-it-iveness : TENACITY. There were a lot of nice down words today.
40. Flowerpot filler : SOIL
46. Christmas tree choice : FIR
48. Seaside home selling point : VIEW
49. Like some poetry : LYRIC
50. Yoga pose : ASANA
51. Japanese, e.g. : ASIAN
53. Fluster : ADDLE
54. Lacquer ingredient : RESIN
55. Wordless okays : NODS
56. On the roof of : ATOP
57. 1970s Chevy subcompact : VEGA. Extreme!
59. Sch. with a Brooklyn campus : LIU. (Long Island University)
62. Hosp. worker : LPN. (licensed practical nurse)