Meas. that becomes three times smaller when you remove its second letter
13A
After
14A
"____ Halloween" (not-so-legendary Adam Sandler movie), or legendary NBA coach Brown)
16A
Common cookie ingredient
17A
Cicatrix
18A
Pass
19A
Fay of the original King Kong
20A
With 36 and 55 Across, American revolutionary firebrand through a noted 19th-early-20th century novelist to a film rebel (36 Across), then through a Rat Pack singer to a noted writer of Theses (55 Across)
23A
Reduplicative Kenyan group that rebelled against British rule
25A
Long-time film critic Pauline
26A
Speed meas. on reel-to-reel tape players
28A
Neither here nor there
30A
Surreptitiously skedaddle
32A
"Flew in from Miami Beach ____" (The Beatles, "Back in the USSR")
33A
"Casablanca" heroine
35A
Piquant
36A
See 20 Across
39A
In court
42A
____nation ("Sail" band)
43A
North Star of "Meatballs" or Walden of "The Parent Trap"
47A
Enthusiastic embrace
49A
___ fish (horseradish delivery device associated with seders)
51A
Circumference component
52A
Idiom follower?
54A
Basement
55A
See 20 Across
58A
SI unit, for short
59A
Jeweler's accessory
60A
Avid singer, on reflection?
63A
"L'___, c'est moi" (apocryphal, not-exactly-humble statement by Louis XIV)
64A
Shoe material for Elvis
65A
"Blimey" alternative
66A
Actress Michelle
67A
Brief signs of success?
68A
Spanish term of endearment meaning "baby"
Verticales
1D
MS-___
2D
Ltd. equivalent
3D
Shoulder blade
4D
Common find at an archeological dig (often in shards)
5D
Heavenly guardians
6D
Bond type, for short
7D
Way to be taken
8D
Proverbially ill
9D
Possible issuer of a 6 Down
10D
Spanish neighborhoods
11D
Remain in place
12D
___ ops
15D
Kennedy or Barrymore
21D
Scottish cap
22D
Female protagonist in My Fair Lady and Hamilton
23D
Pic with agents Kay and Jay
24D
"That's __ from me, dawg"
27D
Spot for slop or sloppy spot
29D
Smarmy
31D
Tentatively slated
34D
NNE opposite
37D
One who has achieved nirvana
38D
Winning slate
39D
JDs' org.
40D
Bug with a liking for lumber
41D
Salted codfish (it's amazing in a stew)
44D
Aaron Judge's foundation
45D
Whence Charlie "never returned," in a classic song protesting a fare increase
46D
What the middle letter of 26 Across stands for
48D
Elec., cable, etc.
50D
"That's disgusting ... get that 49 Across fish away from me!"
53D
Cruciverbalist, at times
56D
Author Philip or director Eli
57D
Hairstyle
58D
Major or minor thing
61D
___ Halen (band whose lead singer was David Lee 56 Down)