Puzzle

 ACROSS

  1 Illegal way to start a trip

  4 Certain Balkans

 10 NYSE debut

 13 Gorilla or gibbon

 14 Elaborate pranks

 15 Indent key

 16 Meme picture format

 17 First New Testament book (Pink Floyd: Last 4 letters + ...)

 18 Bol. neighbor

 19 Northwest Texas native

 21 Compatriot (... first 3 letters)

 22 Long John Silver feature (Bob Marley: Last 3 letters + ...)

 23 Early French settler in Maine

 26 Work units

 27 The Apocalypse (... first3 letters)

 29 Prompt

 30 Farming prefix

 32 Exist

 33 Things that repeat, or a hint to this puzzle's theme

 38 Small songbird

 39 Drunks

 40 Team's possessive

 42 Holds together, MacGyver-style (Carole King: Last 5 letters + ...)

 46 French newborn

 47 In control, as a dog

 48 Lovers' get-togethers (... first 3 letters)

 50 Blacken (Neil Young: Last 3 letters + ...)

 51 Aim for

 54 Payment promise

 55 Virgins of ancient Rome (... first 4 letters)

 57 Part of FWIW

 59 ___ Alamos

 60 Separate, or join

 61 Hiker's guide

 62 Just manage, with "out"

 63 Ruffles have them

 64 Assistant for Santa

DOWN

  1 Fall behind

  2 Meat flavoring

  3 It helps drivers see through glass

  4 P.F. ___'s

  5 Campus military grp.

  6 Vow

  7 Sharp part of a chopping tool

  8 Casual top

  9 U-turn from NNE

 10 Home of Roma

 11 Roll over winnings into a new bet

 12 Delivery people?

 17 West in old films

 20 LA Galaxy's org.

 21 Venomous snake

 22 Muscle targeted by flyes

 24 Do together

 25 Dos for Solange and Jimi Hendrix

 27 Sea eagle

 28 Like Odin

 30 Japanese dog breed

 31 Obtain the highest marks

 34 Oyster-eating mammal

 35 Dawn goddess

 36 Is mid-sentence?

 37 Amount to base a tip on

 41 Hi-___ graphics

 42 Calm

 43 Release, as a fish

 44 Predicate part

 45 Gradually introduced, with "in"

 46 "See ya!"

 48 Scrabble pieces

 49 Monopoly quartet, for short

 52 Antlered male

 53 Prepare for driving?

 55 TiVo predecessor

 56 Whitney who was, aptly, a Yale grad

 58 Beach bottle letters

Solution