puzzle

 ACROSS

  1 It bubbles beneath the surface

  6 Nest sight

  9 One may lead a military drill: Abbr.

 12 Direction indicator

 13 Click the wrong button, e.g.

 14 One-in-a-million

 15 *Simply marvelous

 18 Sailors' affirmatives

 19 Scottish girl

 20 Tiny

 21 Nickname for President Arthur

 22 Mind reader's "power," for short

 23 Fall behind

 25 Sea beast of lore

 27 Nada

 28 O'er there

 29 "Are we there ___?"

 31 Body of water near a cabin, maybe

 34 Unaccompanied

 36 Japanese for "eastern capital"

 38 What's impossible to boil, in a saying

 40 One may be asked to speak

 41 Blue ___ (clear forecast)

 42 Hairdo

 43 Make hazy

 45 Stirs in

 46 PC panic button

 47 Operative

 49 Like some cheeks

 51 "That makes sense now"

 53 Highest point

 54 "Wonder Woman" actress Gadot

 57 Degs. for writers

 58 Scrape (by)

 60 Vestige of the past

 62 Has

 63 *Child who won't touch vegetables, say

 65 Melody for a sitarist

 66 "___ Persisted" (Chelsea Clinton book)

 67 Copy genetically

 68 Before, in poetry

 69 Mars, to Jupiter

 70 Helpful tips

DOWN

  1 Scott Joplin's "___ Leaf Rag"

  2 Precincts

  3 Understand

  4 Shoes with Native roots, briefly

  5 For some time

  6 Cry after seeing a mouse

  7 Became too big for one's britches?

  8 *Thick, creamy breakfast

  9 *Willie Mays' nickname, with "the"

 10 Filled with envy

 11 Word before "anxiety" or after "stress"

 14 Shelving system part

 16 Periods with four seasons

 17 Notorious Roman emperor

 24 *Fond farewell

 26 Picnic pests

 27 Extreme eagerness

 30 Coin flip

 31 Come up short

 32 Causes for conflict

 33 A to B, for one ... or a hint to the word scrambled within each starred clue's answer

 35 Twitch chat chuckle

 37 "Sure"

 39 Loch with a famous monster

 44 Like a mansion

 48 Palindromic bird sound

 50 Public address

 52 Rae who created "Awkward Black Girl"

 54 Joined a conference call

 55 Isn't for us?

 56 Old harplike instruments

 57 "I want seconds"

 59 Sound effect in a canyon

 61 Guinea neighbor

 64 Doll since 1961

solution