Theme: Look At This - Three long entries that, if you add their first word to the end(or FINISH) of PHOTO, you will get a compound word like the unifier.
17A. Penning ads and such : COPY WRITING. PHOTOCOPY.
26A. Mall habitu�'s motto : "SHOP TIL YOU DROP". PHOTOSHOP.
42A. Instrument Bob Dylan was once booed for playing : ELECTRIC GUITAR PHOTOELECTRIC.
56A. Race decided by a camera, or what the start of 17-, 26- or 42-Across literally is : PHOTO FINISH
Argyle here. You don't need me today.
1. Gold medalist's place : FIRST
6. Buddies : CHUMS
11. Use a stun gun on : ZAP
14. Boise's state : IDAHO
15. Saigon's Vietnam War counterpart : HANOI. Map.
16. "__ had it!" : I'VE
19. Wee one : TOT
20. PC key next to the space bar : ALT
21. Buttery and creamy, as pastry : RICH
22. Browsing the Web, say : ON-LINE
24. When doubled, make light of : POOH. "Oh, pooh-pooh!"
25. Church alcove : APSE
32. Ending for micro- or oscillo- : SCOPE
33. Puppy's protest : YELP
34. Big Band __ : ERA
35. Tackle box item : LURE
36. Equine, to a 19-Across : HORSY
38. Odds partner : ENDS
39. Like most codgers : OLD
40. Long-haul rig : SEMI
41. Postal postings : RATES
46. Gold medalist, vis-�-vis competitors : BEST
47. Egyptian snakes : ASPs
48. "Comin' right up" : "IN A SEC"
51. Part of a blind : SLAT
52. "Unbelievable!" : WOW
55. Whopper junior? : FIB
59. Seasonal malady : FLU
60. Crowbar, essentially : LEVER
61. How objects are seen through a mist : DIMLY
62. "Is it soup __?" : YET
63. Skip the announcement, invitations, etc. : ELOPE
64. Old Montreal team : EXPOS. Baseball.
1. Payroll tax acronym : FICA. Federal Insurance Contributions Act(Social Security).
2. Teen favorite : IDOL
3. Totally absorbed : RAPT
4. Hardly outgoing : SHY
5. Line on a tugboat : TOW ROPE
6. Showy to a fault : CHICHI. French.
7. "What __ God wrought?" : HATH. Samuel Morse sent his first telegraph message: �What hath God wrought.� Why that phrase? It was a biblical quote selected by the daughter of one of Morse�s key financial backers. It is a phrase from the Book of Numbers (Numbers 23:23). "Surely there is no enchantment against Jacob, neither is there any divination against Israel: according to this time it shall be said of Jacob and of Israel, What hath God wrought!"
8. Prefix with verse : UNI
9. Game with tiny hotels : MONOPOLY
10. Volunteers (for) : SIGNS UP
11. Penne relative : ZITI. Pasta.
12. Skin So Soft maker : AVON
13. Townshend of The Who : PETE. Musician.
18. Mob disorder : RIOT
23. Was in front : LED
24. Benedict I, e.g. : POPE
25. Affirmative votes : AYEs
26. Oar : SCULL
27. Large crowd : HORDE
28. Emotionally expressive, as poetry : LYRIC
29. Avis __ Car : RENT A
30. Tell the waiter what you want : ORDER
31. Avoid flunking : PASS
32. Gin fizz flavoring : SLOE
36. __ Bernardi, who played Tevye on Broadway : HERSCHEL. Image. Some might remember him as Lt. Jacoby on TV's Peter Gunn.
37. Fail to mention : OMIT
38. Diner sign : EATS
40. Church topper : STEEPLE. Stowe, VT.
41. Scary beach current : RIPTIDE
43. TV network with an eye logo : CBS
44. In great numbers : GALORE
45. "Wild Blue Yonder" mil. group : USAF
48. Far from certain : IFFY
49. River through Egypt : NILE
50. Be contiguous with : ABUT
51. Aerobics accessory : STEP
52. Spineless one : WIMP
53. Norway's capital : OSLO
54. __ and wherefores : WHYS
57. Lacto-__ vegetarian : OVO. A vegetarian who does not eat animal flesh of any kind, but is willing to consume dairy and egg.
58. Put the kibosh on : NIX