puzzle

 ACROSS

  1 Intensify, slangily

  6 House, in Colombia

 10 Ski lodge vessel

 13 Wood for a model plane

 14 Natural magnet

 16 It may help you sleep at night (notice the letter above letter 5)

 18 Word before "lion" or "otter"

 19 Permanent pics

 20 Beef cattle breed

 21 Annoy at work

 24 Achy

 25 ___ Strauss & Co.

 28 Photovoltaic device (... letter 5)

 30 Evil Tolkien creatures

 31 TV exec's plan

 32 Where some commuters unwind (... letter 3)

 36 Stud alternative (... letter 3)

 41 Bottom of a table leg

 43 Sleek: Prefix

 44 Guide to heaven? (... letter 4)

 49 Insect such as a mud dauber

 50 Some primates

 51 Parties with ice cream, perhaps

 53 Step on the gas

 55 Gross

 56 "How exciting!"

 59 Make a 60 a passing score, say ... and what each indicated letter is, in relation to a hidden 3-letter word just below it?

 63 Comfy part of a shoe

 64 Indy entrant

 65 D.C. setting, in the winter

 66 Insignificant

 67 Prize


DOWN

  1 Fundamentals

  2 Like a ram or tom

  3 "Have mercy," for one

  4 D.C. setting

  5 Start of a series

  6 Some diplomats

  7 They play in every Super Bowl broadcast

  8 "Wait a ___!"

  9 Major section of a world atlas

 10 Golden Horde member

 11 Straighten, as a ringlet

 12 Honking birds

 14 Game with a jackpot

 15 Perfect or imperfect

 17 Elliot of the Mamas and the Papas

 21 Part of DJ

 22 Autumn tool

 23 La ___ Tar Pits

 25 High shot from Naomi Osaka

 26 Stretch of history

 27 TiVo ancestor

 29 Navy officer below a capt.

 33 It's south of Eur.

 34 Enormous birds of myth

 35 Lower Manhattan neighborhood

 37 Cornfield cries

 38 Perrins' partner in sauce

 39 Apr. addressee

 40 Appear suddenly, with "up"

 42 Without words

 44 Rejects

 45 Person with renter's insurance

 46 Comment to the audience

 47 Nouveau ___

 48 Seize

 50 Longhorn rival

 52 Swimwear material

 54 Maryland athlete, for short

 56 Killer whale

 57 Cry ___ spilled milk

 58 Drove on a farm?

 60 Buckeyes' sch.

 61 Oui's opposite

 62 Detroit labor org.

solution