6 letters:
amulet

7 letters:
animate, atavist, akvavit, adamant, anapest, agonist, agitate, animist, analyst, adulate, cabinet, aliment, halibut, acetate, manumit, annulet, aquavit

8 letters:
abdicate, activate, patinate, allocate, bassinet, navigate, panelist, aquatint, catenate, validate, laminate, lapidate, graduate, aqueduct, abrogate, annalist, latinist, adjutant, antedate, amputate, tabulate, catapult, vanadate, abnegate, evacuant, capitate, acaudate, adequate, maculate, accident, anapaest, annulate, maledict, annotate, catalyst, salivate, ambulant, fabulist, canonist, paginate, abetment, bandelet, activist, advocate, calamint, aliquant, ambulate, have-not, lapidist

9 letters:
eradicate, jansenist, candidate, canescent, affricate, palpitant, capsulate, coagulate, vaccinate, antiquate, granulate, accumbent, catechist, castigate, abstinent, flatulent, inanimate, acclimate, masticate, exanimate, palpitate, masochist, rabbinate, vacillate, shamanist, astrogate, reanimate, manganate, calibrate, approbate, vacuolate, annulment, staminate, anatomist, fantasist, vacillant, calculate, candlenut, aggravate, crapulent, caliphate, fabricate, fascinate, alchemist, wagon-lit, calvinist, sacrament, sagittate, adumbrate, jactitate, spatulate, tagasaste, analogist, applemint

10 letters:
cantillate, reactivate, invaginate, malfeasant, triacetate, dilapidate, chalcocite, evangelist, cantonment, bafflement, manuscript, inadequate, magistrate, emancipate, classicist, palatinate, pragmatist, battlement, decapitate, inhabitant, flagellant, amalgamate, naturalist, cancellate, antagonist, flagellate, capacitate, passionate, sphacelate, management, desalinate, algebraist, us cabinet, delapidate, reallocate, travelgate

11 letters:
reactionist, philatelist, encapsulate, fractionate, protagonist, strangulate, battlefront, abandonment, nationalist, tobacconist, extrapolate, confabulate, syllabicate, concatenate, perambulate, assassinate, extravagant, triangulate, biocatalyst, recalculate, campanulate, contaminate, contaminant, decoagulant, romanticist, oxalacetate, snaffle bit

12 letters:
anticatalyst, mineralogist, oxaloacetate, intransigent, congratulate, postgraduate, somnambulist, entanglement, somnambulate, permanganate, miscalculate, lead acetate, file cabinet, superannuate, tool cabinet, absquatulate, bantamweight, noncandidate

13 letters:
compassionate, psychoanalyst, zooflagellate, televangelist, procrastinate, decontaminate, ethyl acetate, undergraduate, anticoagulant, antiflatulent, china cabinet, dismantlement, job candidate, sadomasochist

14 letters:
filing cabinet, philanthropist, abstractionist, dinoflagellate, judge advocate, archidiaconate, circumambulate, fatal accident, holy sacrament, market analyst, tintinnabulate

15 letters:
line management, british cabinet, disentanglement, pacific halibut, uncompassionate

16 letters:
devil's advocate, atlantic halibut, industry analyst, medicine cabinet

17 letters:
cerebral aqueduct, cellulose acetate, polyvinyl acetate

19 letters:
inevitable accident

20 letters:
intelligence analyst, plantlike flagellate

21 letters:
united states cabinet