puzzle

 ACROSS

  1 Agcy. that approves vaccines

  4 Florida's second-largest city

  9 Neighbor to a Serb

 14 Acronym for a deep sleep stage

 15 "Sounds likely"

 16 ___ cuisine

 17 Gorilla or gibbon

 18 Is abundant (with)

 19 Did something

 20 Started by banging a gavel, say (In this answer, see letters 8-11)

 23 Opera's "Toreador Song," e.g.

 24 Single man's last statement?

 25 Absurdist art movement

 28 "Baby" or "dance" follower

 29 Subject of a spelling bee contestant's query (... letters 2-5)

 32 A-listers

 34 Unreactive

 35 Knee tear site: Abbr.

 38 Flattering poem

 39 Chasing game

 41 Actress Ruby or Aisha

 42 Trojan War story

 44 Reef substance

 46 Villain who fights the Fantastic Four (... letters 6-9)

 49 Recedes

 53 Detect

 54 Charged atom

 55 Healing plant

 56 What rotates sequentially in 20-, 29-, 46- and 56-Across? (... letters 10-13)

 61 Signal-to-___ ratio

 63 Disappointing used car

 64 Most popular article?

 65 True statements

 66 R&B singer Baker

 67 Pro's opposite

 68 Colgate alternative

 69 Extend a membership

 70 Tilling tool

DOWN

  1 Noisy fight

  2 Leave

  3 2001 title role for Audrey Tautou

  4 Tiny pest

  5 Recognized, for short

  6 Assist in crime

  7 Priyanka Chopra's "Unfinished" and Michelle Obama's "Becoming"

  8 "How peculiar"

  9 Neighbor to Libya

 10 Entered quickly

 11 Furious

 12 Sat for a meal

 13 Fictional coach Lasso

 21 Pool exercises

 22 Kanga's child

 26 Urgent

 27 Add a little something to the pot?

 29 Crumpled piece of paper

 30 Fool's gold, e.g.

 31 Capital of Latvia

 33 Type of list

 35 Assists

 36 Hoofbeat sound

 37 Candy that's often twisted

 39 As well

 40 Upper line on a stick figure

 43 Bears witness (to)

 44 Have a meeting

 45 Be in charge

 47 Home of Brazil's Sugarloaf Mountain

 48 Currency in Liberia or Canada

 50 Irregular stain

 51 Insincere crying sound

 52 Untroubled

 57 Waistcoat's American equivalent

 58 "Sign me up!"

 59 Jot down

 60 Nibble like a rodent

 61 Sports org. with Lions and Bears

 62 Rowboat steerer

solution