| Under-the-sink installation | 27 |
| Under-the-sink scourers | 23 |
| Under-the-table action | 22 |
| Under-the-table activity | 24 |
| Under-the-table diversion | 25 |
| Under-the-table flirtation | 26 |
| Under-the-table payment | 23 |
| Under-the-table payments | 24 |
| Under-the-table promotion | 25 |
| Under-the-table things | 22 |
| Under-the-weather-looking | 25 |
| Under-the-window performance | 28 |
| Under-the-window routine | 24 |
| Under-water detection aid | 25 |
| Underachiever's motto? | 26 |
| Underage drinker in Lincoln? | 28 |
| Underage drinker's item | 27 |
| Underage temptation, slangily | 29 |
| Underappreciated laborer | 24 |
| Underbosses' bosses | 23 |
| Undercard fight, for short | 26 |
| Undercoat applications | 22 |
| Underconfident utterances | 25 |
| Undercooked meat danger | 23 |
| Undercooked, as an egg | 22 |
| Undercover agent of a sort | 26 |
| Undercover agent's cover? | 29 |
| Undercover agent's wear | 27 |
| Undercover agent, in slang | 26 |
| Undercover cop of 1970s TV | 26 |
| Undercover cop, at times | 24 |
| Undercover cop, perhaps | 23 |
| Undercover drug agents | 22 |
| Undercover group: Abbr. | 23 |
| Undercover police operation | 27 |
| Undercover worker, perhaps | 26 |
| Undercover, informally | 22 |
| Underdeveloped countries | 24 |
| Underdeveloped nations | 22 |
| Underdog in a certain ring | 26 |
| Underdog playoffs participant | 29 |
| Underdog winner over T.E.D. | 27 |
| Underdog with a chance | 22 |
| Underdog's achievement | 26 |
| Underdog's fastener? | 24 |
| Underdog's victory | 22 |
| Underdog's win, e.g. | 24 |
| Underdogs may beat them | 23 |
| Underdogs' victories | 24 |
| Underfooting for Fleming | 24 |
| Underfootings for dignitaries | 29 |
| Undergarment fitting device? | 28 |
| Undergarment specification | 26 |
| Undergarment, for short | 23 |
| Undergo a change of habit? | 26 |
| Undergo a chemical change | 25 |
| Undergo chemical change | 23 |
| Undergo gradual change | 22 |
| Undergo natural selection | 25 |
| Undergo training, perhaps | 25 |
| Undergo without yielding | 24 |
| Undergoes a chemical change | 27 |
| Undergoes a transformation | 26 |
| Undergoing severe trials | 24 |
| Undergrad course of study | 25 |
| Undergrad course, briefly | 25 |
| Undergrad degrees: Abbr. | 24 |
| Undergrad's bugbear | 23 |
| Undergrads' degrees | 23 |
| Undergraduate law deg. | 22 |
| Underground art site in Spain | 29 |
| Underground artists, maybe | 26 |
| Underground blast, perh. | 24 |
| Underground burial places | 25 |
| Underground burial site | 23 |
| Underground coal source | 23 |
| Underground crop storage area | 29 |
| Underground dance party | 23 |
| Underground discoveries | 23 |
| Underground explosions | 22 |
| Underground folklore creature | 29 |
| Underground hip-hop release | 27 |
| Underground infiltrator | 23 |
| Underground installation | 24 |
| Underground launch site | 23 |
| Underground mag of the 1960s | 28 |
| Underground meeting place | 25 |
| Underground missile site | 24 |
| Underground molten rock | 23 |
| Underground movement leader? | 28 |
| Underground music genre | 23 |
| Underground part of a plant | 27 |
| Underground passageway | 22 |
| Underground petroleum source | 28 |
| Underground plant part | 22 |
| Underground plant parts | 23 |
| Underground plant supports | 26 |
| Underground protection | 22 |
| Underground Pueblo chamber | 26 |
| Underground railroad leader | 27 |