| Underground railroad | 20 |
| Underground Railroad "conductor" | 42 |
| Underground Railroad "passenger" | 42 |
| Underground Railroad destination | 32 |
| Underground railroad leader | 27 |
| Underground Railroad leader and Union spy | 41 |
| Underground Railroad traveler | 29 |
| Underground Railroad user | 25 |
| Underground railways of Paris and D.C. | 38 |
| Underground rapper Brother ___ | 30 |
| Underground rapper ___ Rock | 27 |
| Underground rapper's demo | 29 |
| Underground rarity? | 19 |
| Underground resource | 20 |
| Underground riches | 18 |
| Underground rider, probably | 27 |
| Underground rock source | 23 |
| Underground rock? | 17 |
| Underground rodent | 18 |
| Underground role of '50s TV? | 32 |
| Underground room | 16 |
| Underground route | 17 |
| Underground runner | 18 |
| Underground sources of income | 29 |
| Underground stem | 16 |
| Underground stinker | 19 |
| Underground stop | 16 |
| Underground storage spot | 24 |
| Underground story | 17 |
| Underground strikes | 19 |
| Underground support | 19 |
| Underground supporter | 21 |
| Underground supporter? | 22 |
| Underground system | 18 |
| Underground systems | 19 |
| Underground tombs | 17 |
| Underground trains | 18 |
| Underground transport | 21 |
| Underground transport systems | 29 |
| Underground transportation | 26 |
| Underground treasure | 20 |
| Underground treasures | 21 |
| Underground tunneler | 20 |
| Underground type | 16 |
| Underground vault | 17 |
| Underground vegetable | 21 |
| Underground vegetable with edible greens | 40 |
| Underground vein | 16 |
| Underground waste | 17 |
| Underground water carrier | 25 |
| Underground water source | 24 |
| Underground water sources | 25 |
| Underground water tank | 22 |
| Underground way | 15 |
| Underground wealth | 18 |
| Underground work site | 21 |
| Underground worker | 18 |
| Underground worker, perhaps | 27 |
| Underground workers | 19 |
| Underground workplace | 21 |
| Underground ___ | 15 |
| Underground-railroad cargo | 26 |
| Undergroundgrowth | 17 |
| Undergrown | 10 |
| Underhand | 9 |
| Underhand arrest maneuver | 25 |
| Underhand doings | 16 |
| Underhand ploy | 14 |
| Underhand throw | 15 |
| Underhand toss | 14 |
| Underhand? | 10 |
| Underhanded | 11 |
| Underhanded activities | 22 |
| Underhanded attack | 18 |
| Underhanded bum | 15 |
| Underhanded change | 18 |
| Underhanded change, slangily | 28 |
| Underhanded commercial ploy | 27 |
| Underhanded course of action | 28 |
| Underhanded fellow | 18 |
| Underhanded fling | 17 |
| Underhanded Massive Attack song? | 32 |
| Underhanded one | 15 |
| Underhanded or duplicitous | 26 |
| Underhanded plan | 16 |
| Underhanded schemer | 19 |
| Underhanded schemes | 19 |
| Underhanded sort | 16 |
| Underhanded tactic | 18 |
| Underhanded throw | 17 |
| Underhanded type | 16 |
| Underhanded types | 17 |
| Underhanded, in a way | 21 |
| Underhanded, to put it nicely | 29 |
| Underhandedly clever | 20 |
| Underhandedly obtain | 20 |
| Underlayer of skin | 18 |
| Underlies | 9 |
| Underline | 9 |
| Underline alt. | 14 |