3 letters:
cup, pup, sup, yup

5 letters:
getup, krupp, letup, pinup, setup, shtup

6 letters:
backup, blowup, burnup, cockup, dustup, eggcup, eyecup, get-up, holdup, hookup, kickup, lay-up, lineup, linkup, lockup, makeup, markup, mix-up, pickup, pileup, pin-up, pop-up, pushup, put-up, run-up, selkup, sendup, set-up, sit-up, slipup, tcp ip, teacup, tie-up, tip-up, tittup, tossup, turnup, washup, wickup, windup

7 letters:
back-up, bang-up, beat-up, breakup, brushup, buildup, bust-up, call-up, checkup, chin-up, cleanup, closeup, cock-up, coverup, dial-up, egg cup, elf cup, eye cup, foul-up, goldcup, grownup, hang-up, high-up, kingcup, lash-up, line-up, made-up, make-up, mess-up, mock-up, nosh-up, paid-up, pent-up, pick-up, piss-up, pull-up, push-up, rave-up, roll-up, roundup, shakeup, slap-up, slip-up, speedup, standup, startup, step-up, stickup, take-up, toss-up, tune-up, used-up, walk-up, warm-up, wickiup, wind-up

8 letters:
balls-up, belly-up, blown-up, booze-up, built-up, close-up, cover-up, crack-up, dice cup, dried-up, flare-up, followup, frame-up, grown-up, heads-up, mixed-up, paste-up, press-up, punch-up, seven-up, shake-up, shape-up, smash-up, snarl-up, stand-up, start-up, stuck-up, whitecup, wolf pup, write-up

9 letters:
acorn cup, beaten-up, beefed-up, blood cup, bottom-up, brown cup, buttercup, change-up, death cup, dixie cup, fairy cup, follow-up, fucked-up, grace cup, heaped-up, higher-up, hopped-up, jumped-up, marked-up, optic cup, paper cup, pumped-up, rolled-up, runner-up, sweet cup, washed-up

10 letters:
churned-up, coffee cup, dressed-up, golden cup, loving cup, pick-me-up, stopped-up, trumped-up, washing-up

11 letters:
painted cup, puckered-up, queen's cup, scarlet cup, stirrup cup

12 letters:
drinking cup, mustache cup, trash pickup

13 letters:
champagne cup, drain the cup, measuring cup, moustache cup

14 letters:
black felt cup, crystal pickup, garbage pickup, johnny-jump-up, tall buttercup

15 letters:
computer backup, giant buttercup, medical checkup, water buttercup

16 letters:
common buttercup, meadow buttercup, temporary hookup

17 letters:
bermuda buttercup, western buttercup

18 letters:
creeping buttercup

19 letters:
charred pancake cup, sagebrush buttercup

20 letters:
tall field buttercup

3 letters:
hub, nub, pub, sub, rub, cub, dub, tub

4 letters:
club, stub, snub, grub, drub

5 letters:
shrub, scrub

8 letters:
wolf cub, bear cub, lion cub, subshrub

9 letters:
golf club, tiger cub, glee club, ball club, farm club, hunt club

10 letters:
yacht club, check stub, chess club, lions club, slate club

11 letters:
indian club, ticket stub, supper club, rotary club, golden club, grainy club, jockey club, racket club, rowing club, sweet shrub, tennis club

12 letters:
country club, pepper shrub, service club

13 letters:
baseball club

15 letters:
flowering shrub

16 letters:
strawberry shrub

19 letters:
soldier grainy club