Or search: aver, avow, doom, lull, swan, tick, cinch, swear, vouch, affirm, assert, ensure, insure, pledge, plight
1 Syllable: S
boor, cure, jure, lure, Moor, Moore, Moore's, Moors, Muir, nur, pure, sure, tour, ture, your
2 Syllables: SU
detour
2 Syllables: US
abjure, allure, assured, assures, brochure, demure, endure, ensure, impure, insure, inured, manure, mature, obscure, procure, reassure, secure, unsure
3 Syllables: UUS
immature, premature
4 Syllables: UUUS
entrepreneur

Found 37 words across 5 groupings. Skipped 25 excess words of a similar stem.