| Uncomfortable airline inconvenience | 35 |
| Uncomfortable guests at a wedding, maybe | 40 |
| Uncomfortable underclothing condition | 37 |
| Uncommon source of music nowadays | 33 |
| Uncommon sources of music nowadays | 34 |
| Uncommonly late start to the workday | 36 |
| Uncomplaining in the face of adversity | 38 |
| Uncompleted Orson Welles film project | 37 |
| Unconcerned with right and wrong | 32 |
| Unconditional Broadway hit: 1939–47 | 42 |
| Unconfident lovers might pick them | 34 |
| Unconscious gaze (with the preceding space) | 43 |
| Unconscious urge to go to heaven? | 33 |
| Uncontested, as a late-game hockey goal | 39 |
| Uncontested, like some hockey goals | 35 |
| Uncontrollably cutting down trees? | 34 |
| Uncontrolled development around a city | 38 |
| Uncontrolled nuclear fusion site | 32 |
| Uncontrolled, short, jerky motion | 33 |
| Unconventional artists, in slang | 32 |
| Unconventional delivery of supplies | 35 |
| Unconventional merchandise quantity | 35 |
| Uncouth Kiss song off "Revenge" | 41 |
| Uncovered exam at some hospitals | 32 |
| Uncredited in 'Bartlett's' | 38 |
| Unctuous preparation for external use | 37 |
| Undecided, in some listings (abbr.) | 35 |
| Undefined mathematical operation | 32 |
| Undeliverable letter, in post-office talk | 41 |
| Undeliverable letter, to a postal worker | 40 |
| Under an assumed name, informally | 33 |
| Under restraint, after "on" | 37 |
| Under the "alfluence of incohol" | 42 |
| Under the influence, with 'out' | 39 |
| Under the least favorable circumstances | 39 |
| Under the most favorable circumstances | 38 |
| Under the most favorable conditions | 35 |
| Under ___ (Pledge of Allegiance phrase) | 39 |
| Under-the-bridge folklore villain | 33 |
| Under-the-counter ne'er-do-wells? | 37 |
| Under-the-hood knock source, perhaps | 36 |
| Underage child of a military officer? | 37 |
| Undercover operation to trap a letter? | 38 |
| Undercover Playboy bunny of 1963 | 32 |
| Undercover surveillance vehicle, perhaps | 40 |
| Underdog's motivation (Part 1) | 34 |
| Underdog's motivation (Part 2) | 34 |
| Underdog's motivation (Part 3) | 34 |
| Undergarment that makes scaly legs look good? | 45 |
| Undergarments that allow for air flow? | 38 |
| Undergarments that show a little of the chest | 45 |
| Undergo a chemical transformation | 33 |
| Undergo an uncomfortable phase of infancy | 41 |
| Undergo transformation, as one image into another | 49 |
| Undergoes again, as an experience | 33 |
| Undergoes liquefaction, as a gel | 32 |
| Undergrad curriculum for a doctor-to-be | 39 |
| Undergrads' Greek leadership society | 40 |
| Undergraduate degree, to a pilot | 32 |
| Underground cartoonist's products | 37 |
| Underground experiment, for short | 33 |
| Underground film actress Sedgwick | 33 |
| Underground place to meet your friends? | 39 |
| Underground Railroad "conductor" | 42 |
| Underground Railroad "passenger" | 42 |
| Underground Railroad destination | 32 |
| Underground Railroad leader and Union spy | 41 |
| Underground railways of Paris and D.C. | 38 |
| Underground role of '50s TV? | 32 |
| Underground vegetable with edible greens | 40 |
| Underhanded Massive Attack song? | 32 |
| Underlying pattern of the universe | 34 |
| Underlying principle of the universe | 36 |
| Underlying theme of "Se7en" | 37 |
| Underperforming investment, slangily | 36 |
| Undersized bats and gloves, e.g. | 32 |
| Understand now, as someone's tricks | 39 |
| Understand speech without hearing | 33 |
| Understand spoken words without hearing them | 44 |
| Understand the works of Courbet? | 32 |
| Understand, according to Robert Heinlein | 40 |
| Understandings of others' situations | 40 |
| Understudies for a star of "The Piano"? | 49 |
| Underthing that's part of a bleeped phrase? | 47 |
| Underwater "wolf pack" | 32 |
| Underwater creature whose males give birth | 42 |
| Underwater detection instruments | 32 |
| Underwater England/France connection | 36 |
| Underwear promoted by Michael Jordan | 36 |
| Underwear that never needs washing? | 35 |
| Underwood and Studdard, affectionately | 38 |
| Underworld entrance, to an Italian | 34 |
| Underworld group, with "the" | 38 |
| Underworld overlord, in crookspeak | 34 |
| Undesirable development around a city | 37 |
| Undesirable one, to Theodore Cleaver | 36 |
| Undesirable result of making a pass?: Abbr. | 43 |
| Undeveloped but potentially useful | 34 |
| Undisputed leader at drawing walks? | 35 |
| Undoer of "ritardando" | 32 |