puzzle

 ACROSS

  1 Possesses

  4 Baby bird?

  9 "Hey you!"

 13 Start to drip, as ice cream

 14 Prepare for a selfie, perhaps

 15 Irritate

 16 ___ Emhoff, fashionable Second Family member

 17 Movie's sound portion

 18 A party to

 19 "Think different" and "Just Do It"

 21 Fails during a crucial moment

 23 ___ lane

 24 '90s Poet Laureate Dove

 26 "The Americans" star Russell

 27 Biosphere component

 30 Zero, in soccer

 33 Flail

 35 Like a sorry sight

 36 Taj Mahal's city

 37 Grilling spot?

 39 Cheer on

 41 1975 Wimbledon winner Arthur

 42 Cosmo, e.g.

 44 Enemy of an enemy, maybe

 45 Peg for a golf ball

 46 Play with fire

 48 Substandard

 50 Silverstein who wrote "The Giving Tree"

 51 Site for experimentation, briefly

 54 Cured sausage

 56 Congresswoman Tlaib

 58 Spans sometimes named for presidents

 59 Apple product

 62 Burnt ___ (barbecue morsels)

 63 They scurry ... or scroll

 64 Fontdesigned in 1982

 65 Matures

 66 Pi Day follower

 67 Very mean

 68 Acid Tests drug

DOWN

  1 Greeting from Lionel Richie or Adele?

  2 Scattered everywhere (In this clue's answer, notice letters 3 to 6)

  3 Deer with a rack

  4 Like the Rough Riders' war (... 6 to 10)

  5 Reliable

  6 Ref. to which "adorkable" was introduced in 2020

  7 Camping gear co-op

  8 Punched out at lunch, maybe (... 10 to 13)

  9 Earlier

 10 Bad premonitions ... or a hint to 2-, 4- and 8-Down

 11 ___ gin fizz

 12 X X X

 13 Holey material

 20 Surfaced

 22 Fashion line?

 25 One of a mule's parents

 28 Gumshoe's undertaking

 29 ___ Heel State (North Carolina)

 31 Golfer's alternative to a wood

 32 Pig fat

 33 Not this

 34 Kinky item in a yard

 36 Quarreling

 38 Scottish cap

 40 Apt exams to take in dental school?

 43 Navigation device, briefly

 46 Male turkey or cat

 47 Danger

 49 Camels' watering holes

 52 Used an abacus

 53 "Upright" instrument

 54 Big rig

 55 Like much of New Mexico's climate

 57 Get better

 60 Lyricist Gershwin

 61 Prefix for "union"

solution