1.  2. 3.   g 4. 5. 6.  7.  8. 9. g 10.
  g 11.   g 12.     g   g 13.  14.  
  g 15.  16.   g g 17.     g 18.   
  g g 19.   20. g   g   g g g   g
g 21. 22.   g 23.    g 24.   25. 26.   g
27. g   g 28. g   g 29. g   g 30.   g 31.
32. 33. g 34.  35.       g   g 36.  
37.   g g 38.    g   g g 39.     
40.  41. g   g g 42. g 43. g 44.   g   g
45.   46. g 47.         g 48. 49.
g   g   g   g   g   g   g g g  
50.    51.    g 52.  53. g 54.    
g   g 55.    g 56. g 57.     g g  
58.  59. g 60.     g g   g 61.  62.  
  g   g 63.   g   g 64.  65.   g   g
  g 66.         g 67.     

THE BIG CHAIN

With punctuation as shown, the following formations are (mostly) (fairly) normal expressions ...

1→ 28↓

28↓ 13→

13→ 27↓

27↓ 14↓ 22↓

14↓ 22↓ 10↓ 7↓

7↓ 45→

45→ 60→

60→ 34→

34→ 47↓

47↓ 54↓

54↓ 19→

19→ 1↓

1↓ 53↓

53↓ 10↓ 36↓

36↓ 33↓

33↓ 30→ 10↓ 3↓

3↓-50→

50→ 54→

54→ 4→

4→ 29↓

29↓ 6↓

6↓ 30→ 12↓ 47→

47→ 66→

66→ 67→

67→ 9↓

9↓-2↓-39↓

39↓ 20↓

20↓ 44→ 10↓ 24→

24→ 61→

61→ 43↓

43↓ 58↓

58↓-31↓

31↓ 1→

And the remaining "normal" clues ...

ACROSS

11. Quickly close in on Enron (2.)

12. Repetitive toy (2-2)

15. Repetitive memory (4)

17. Oddly near "Yes", they are anything but (4)

18. To 61-Across, an extremity (3)

21. Muscles to help stop a car (3)

23. Free Friday offering (3)

32. = 65-Down (2)

36. Male subject (2)

37. Briefly mount, even smite (2.)

38. Shy of company, this confused generation (3)

39. Virtue of timer arrangement (5)

40. Take back "take King", take ... (3)

48. ... take Bishop. Big throw, and ... presto! (2)

52. Host of big street party, not quite civil unrest (3)

55. Coat for returning scoundrel (3)

57. Claim rave review (4)

58. Could contribute to schism (3)

63. Leading note of note's ending (2)

64. Numerous notes, in my ear I assume (4)

DOWN

4. Dominant note of esoterica (2)

5. At heart of "No"s, it is anything but (2)

8. Briefly threaten King and Church (2.)

16. Party half of 15-Across (2)

25. Do ambitions provide leaders? (6)

26. Long wave of shellfish (1.1.)

35. One of 17-Across in knowledge (2)

41. Not backwards, not negative, not away (2)

42. Try to find out, as King (3)

46. Wager time after wordplay (4)

49. Course, or part (5)

51. A test after mixing? (5)

56. One time, not a long time, one race (4)

59. Some moose heard from another herd (3)

62. Dubious, like this word? (3)

64. Promotion time (2)

65. = 32-Across (2)