These are NPL-style flats. They each have 14 words, and each has a base part that refers to one of the 14 senses of the adjective “flat”, as hinted by the title and the flavortext.
Their solutions are as follows:
| Flat def. sense | “Flat” base | Other part of base | Wordplay type | Original flat |
|---|---|---|---|---|
| 6 | FIXED | FAXED | SECOND LETTER CHANGE | Our hi-pri docs cannot be CLAIR. ’Til CHAIR, we must send mail by air. |
| 2 | HORIZONTAL | ABHOR, CHORIZO, DENTAL | TELESTICHAL ENIGMA | Hate open crab? Use sausage anchor. With teeth, grin wide, Not up to rancor. |
| 4 | LEVEL | OLIVE OIL | CONSONANTCY | Canola is not my suggested choice grease. Instead, extra-virgin GAS ups food’s taste GEESE. |
| 9 | LOW | OWL | HEAD-TO-TAIL SHIFT | Keep barn CATSs SCAT on gloves, not sky. In jesses, birds won’t even fly. |
| 12 | MATTE | MATTER | CURTAILMENT | The first two cans’re gloss, but then The pressing TEND: The third one’s TEN! |
| 7 | MONOTONOUS | SUM | REVERSED PALINDROME DELETION | The drone goes on too long and DIVINE. In END, I execrate its whine. |
| 8 | OFF-KEY | COFFEE | SOUND SHIFT | Beer, tea, black VIEW all serve to move A singer’s voice to sounding YOU’VE |
| 1 | PROSTRATE | PROSTATE | DELETION | I do suggest for older guys To lay EYRES while doc checks your EYES |
| 5 | SHORT-HEELED | SH or the E LED | REBUS | I’ve spools and kittens, leather pumps—I think that SOL shoes are for chumps. |
| 3 | SMOOTH | MOOT | TERMINAL DELETION | They put up new rugs that are BLAH. That older ones were rough’s LA. |
| 14 | STABLE | SEAT BELT | LETTER BANK | My horse should have a ROEHRICH? Fair. I’m clumsy on beasts from a CO-HEIR. |
| 11 | TAUT | TAUGHT | HOMONYM | We’re BARE to string it BEAR to shoot, Avoiding your new shoes to boot! |
| 13 | TRACK | RACK | BEHEADMENT | To PAT down vintners, one just scans For wine ATs detailed in floor plans. |
| 10 | UNINFLECTED | UNINFECTED | DELETION | With negative culture and unchanging voice, I’m BACH and my BATCH dialect’s by choice. |
Order by the sense of the adjective “flat” in m-w.com (or the print 11th Collegiate Dictionary) and take the nth word of each flat, where n is the sense of “flat” in each flat. You get:
I open up my leather CHAIRAnd move in my new third floor CO-HEIRThe cuewords clue this is a consonantcy. The solution is APARTMENT/PORTMANTEAU. Take the non-“flat” one to get the answer PORTMANTEAU.