1: Itching (to)

6: Segments of history

10: PC software

14: Prevent, with 'off'

15: Hit hard

16: Joint inflammation

17: Infant's distress

18: Just

19: Earthenware jar

20: Hazarding a guess: doughy metaphysician?

23: Nurse, as a zombie

24: Toss back

25: Menlo Park monogram

26: Can opener?

29: Boil fluid

31: Matzo meals

33: One who knows the score

37: Sprawling narrative

38: In the past

39: Knock preceder

43: Organizations with Greek letters

48: Wicker stick

51: '___ appétit!'

52: Flight from justice

53: Long time

54: Wails

57: Block up

59: What an astronaut experiences in space

64: Butler, for Gable

65: Glissando instrument

66: Part of the small intestine

68: Burn soother

69: Upper hand

70: Lions and Tigers and Bears

71: Get into a spot?

72: Woodwind requirement

73: Cries out

1: PC bailout

2: Capping

3: Festive affair

4: Devilish doings

5: Proof of purchase

6: Black, to a bard

7: Flat rates?

8: Give permission for

9: Wave maker

10: Bug-eyed

11: Civil

12: Watch brand

13: Montana and Washington

21: Important work

22: Type of arch

26: Balaam's mount

27: Resort hotel

28: Not share

30: 'Flee, feline!'

32: 'Blast!'

34: Piece of water sport equipment

35: Historical period

36: Gather on a surface

40: Diddly-squat

41: Afternoon brew

42: Mao follower?

44: Impetuous

45: '___ Day in Paradise' (1998 Melanie Griffith movie)

46: Acknowledges silently

47: Folly

48: Cover over

49: Dark circle

50: Sartorial expert

55: Cutter

56: Twill weave

58: Free-for-all

60: Nerd's friend

61: Stepped on it

62: Flippered fish fancier

63: Drainage reservoir

67: Mag. submissions