| Underground Railroad traveler | 29 |
| Underground Railroad user | 25 |
| Underground rapper ___ Rock | 27 |
| Underground rapper's demo | 29 |
| Underground rider, probably | 27 |
| Underground rock source | 23 |
| Underground sources of income | 29 |
| Underground storage spot | 24 |
| Underground supporter? | 22 |
| Underground transport systems | 29 |
| Underground transportation | 26 |
| Underground water carrier | 25 |
| Underground water source | 24 |
| Underground water sources | 25 |
| Underground water tank | 22 |
| Underground worker, perhaps | 27 |
| Underground-railroad cargo | 26 |
| Underhand arrest maneuver | 25 |
| Underhanded activities | 22 |
| Underhanded change, slangily | 28 |
| Underhanded commercial ploy | 27 |
| Underhanded course of action | 28 |
| Underhanded or duplicitous | 26 |
| Underhanded, to put it nicely | 29 |
| Underlined text, perhaps | 24 |
| Underling of Fearless Leader | 28 |
| Underling of the 11th century | 29 |
| Underling's acquiescence | 28 |
| Underling's assignment | 26 |
| Underlings follow them | 22 |
| Underlying explanation | 22 |
| Underlying form of a word | 25 |
| Underlying system of beliefs | 28 |
| Undermine, as confidence | 24 |
| Underminer of principles | 24 |
| Undermines, as support | 22 |
| Underpass drainage channels | 27 |
| Underpay a comic actor? | 23 |
| Underpinnings of Windows 1.0 | 28 |
| Undersea craft (Abbr.) | 22 |
| Undersea explorer Jacques | 25 |
| Undersea party pooper? | 22 |
| Undersea prowler, briefly | 25 |
| Undershirt, in Britain | 22 |
| Underside of some shoes | 23 |
| Underside-of-the-desk gunk | 26 |
| Undersides of overhangs | 23 |
| Undersized flower girl? | 23 |
| Undersized pickpocket? | 22 |
| Undersized stock trade | 22 |
| Understaffed situation | 22 |
| Understand incorrectly | 22 |
| Understand intuitively | 22 |
| Understand or be punished | 25 |
| Understand President Bush | 25 |
| Understand the difference | 25 |
| Understand the true nature of | 29 |
| Understand what's implied | 29 |
| Understand without hearing | 26 |
| Understand, as a language | 25 |
| Understand, in hippie lingo | 27 |
| Understand, in sci-fi jargon | 28 |
| Understand, in sci-fi lingo | 27 |
| Understand, informally | 22 |
| Understand, instinctually | 25 |
| Understand, to hipsters | 23 |
| Understand, to Kerouac | 22 |
| Understanding between nations | 29 |
| Understanding comments | 22 |
| Understanding of a sort | 23 |
| Understanding response | 22 |
| Understanding responses | 23 |
| Understanding utterance | 23 |
| Understanding, of sorts | 23 |
| Understands on a deep level | 27 |
| Understands the matter | 22 |
| Understands the operation | 25 |
| Understands the point of | 24 |
| Understands the problem | 23 |
| Understands, as a joke | 22 |
| Understands, as sheet music | 27 |
| Understands, to a Scot | 22 |
| Understatement for effect | 25 |
| Understood archaeology? | 23 |
| Understood archeology? | 22 |
| Understood by a select few | 26 |
| Understood by only a few | 24 |
| Understood by very few | 22 |
| Understood one did wrong | 24 |
| Understood what one did wrong | 29 |
| Understood, as a punch line | 27 |
| Understudy's crime? | 23 |
| Understudy's dream | 22 |
| Understudy's study | 22 |
| Undertake halfheartedly | 23 |
| Undertake legal recourse | 24 |
| Undertake precipitately | 23 |
| Undertaker's purchase | 25 |
| Undertakes without permission | 29 |
| Undertaking, in Britain | 23 |