The answer is SIXTEENTH AMENDMENT
The corresponding square is INCOME TAX
   by Roger Barkan

This is an "Anguished English" puzzle, where each of the lines sounds
pretty much like a common phrase.  Well, except in each line, there's
an extra word thrown in.  Taking the extra words from consecutive
lines forms a new Anguished English phrase.

Every few lines produces a new second-level phrase.  Both the
first-level phrases and the second-level phrase share a common theme--
for example, te first four lines are all magazines.

GNASHING (SUPPORT) ALGAE OKRA FAKE           = National Geographic
RITA STY (SILLY) JUST                        = Reader's Digest
GODOT SKI PANG (STRAY)                       = Good Housekeeping
GAUZE MOPE HOLLY TEN (DEAD)                  = Cosmopolitan
(SUPPORT SILLY STRAY DEAD)                   = SPORTS ILLUSTRATED

COKE (GOLF) OCEAN KNELL                      = Coco Chanel
A STALE OTTER (INCLINE)                      = Estee Lauder
(GOLF INCLINE)                               = CALVIN KLEIN
			                     
(SOW) BUS IFFY COLANDER                      = Pacific Islander
MEAD ELISE (FIRM) TURN                       = Middle Eastern
YOU ROPE (ARROGANT) IAN                      = European
(SOW FIRM ARROGNAT)                          = SOUTH AMERICAN

ANTSY ATTIC LEEK (TREE)                      = Hanseatic League
HACKS (POLLEN) HASP OURS                     = Axis Powers
WORE (TAUNT) SOP ACT                         = Warsaw Pact
(TREE POLLEN TAUNT)                          = TRIPLE ENTENTE
			                     
(HAY) BANDIT ONYX KALE                       = pentatonic scale
DIMES EGG (THIN) NURTURE                     = time signature
WIN (OAT) DANCE DRUMMOND                     = wind instrument
(HAY THIN OAT)                               = EIGHTH NOTE

(THOUGH) FUSS CODA COMMA                     = Vasco Da Gama
EMERY (WRYER) COVE ASP HOOCHIE               = Amerigo Vespucci
LEAVER (DOLL) AXON                           = Leif Ericson
(THOUGH WRYER DOLL)                          = THOR HEYERDAHL

(HEARSE) HAND RAH MUTTER                     = Andromeda
SAD JITTERY (SUM) ASS                        = Sagittarius
GROAN ABHOR HE (AGER) ALICE                  = Corona Borealis
(HEARSE SUM AGER)                            = URSA MAJOR

HASNT BARGAINS (BURN) HARDEN DEEP RAN SUPPLE = Heisenberg Uncertainty Principle
SEND RIBBIT ALL (JULIO) FOURS                = centripetal force
I.D. (FACT) HELGA SLAW                       = Ideal Gas Law
(BURN JULIO FACT)                            = BERNOULLI EFFECT

RELEARN (NUMB) ALLEY SASS                    = real analysis
LENNY URAL JABBER (BIRTH)                    = linear algebra
DIVA RANGE ALEC (ERIE) WEIGH SHINS           = differential calculus
(NUMB BIRTH ERIE)                            = NUMBER THEORY

LESS SAFE HEIR (AUNT)                        = laissez-faire
FADER (RENEW) CALM PLEA                      = fait accompli
(ANT RENEW)                                  = ENTRE NOUS
			              
(MARVEL) HOUR DUCK HOSE ELL                  = Howard Cosell
CREE SPERM (BIRD) INN                        = Chris Berman
(MARVEL BIRD)                                = MARV ALBERT

ALLAH (KNEE) FART WHIZZED                    = Oliver Twist
MARRED INCHES ILL (COLA) WHIT		     = Martin Chuzzlewit
DAFFY TICK HOPPER (SNEAK) FILLED	     = David Copperfield
EBONIES HUSK ROUGE (ALBEE)                   = Ebeneezer Scrooge
(KNEE COLA SNEAK ALBEE)                      = NICHOLAS NICKLEBY

Once you've found all the second-level phrases, take the first letter
from each word.  You'll get "SICK SATEEN THUMB ENTENMANN", which is
one last Angusihed English clue for the answer: SIXTEENTH AMENDMENT.