| Underground systems | 19 |
| Underground system | 18 |
| Underground supporter? | 22 |
| Underground supporter | 21 |
| Underground support | 19 |
| Underground strikes | 19 |
| Underground story | 17 |
| Underground storage spot | 24 |
| Underground stop | 16 |
| Underground stinker | 19 |
| Underground stem | 16 |
| Underground sources of income | 29 |
| Underground runner | 18 |
| Underground route | 17 |
| Underground room | 16 |
| Underground role of '50s TV? | 32 |
| Underground rodent | 18 |
| Underground rock? | 17 |
| Underground rock source | 23 |
| Underground rider, probably | 27 |
| Underground riches | 18 |
| Underground resource | 20 |
| Underground rarity? | 19 |
| Underground rapper's demo | 29 |
| Underground rapper ___ Rock | 27 |
| Underground rapper Brother ___ | 30 |
| Underground railways of Paris and D.C. | 38 |
| Underground Railroad user | 25 |
| Underground Railroad traveler | 29 |
| Underground Railroad leader and Union spy | 41 |
| Underground railroad leader | 27 |
| Underground Railroad destination | 32 |
| Underground Railroad "passenger" | 42 |
| Underground Railroad "conductor" | 42 |
| Underground railroad | 20 |
| Underground purchases | 21 |
| Underground Pueblo chamber | 26 |
| Underground protection | 22 |
| Underground plotters | 20 |
| Underground plant supports | 26 |
| Underground plant parts | 23 |
| Underground plant part | 22 |
| Underground place to meet your friends? | 39 |
| Underground petroleum source | 28 |
| Underground passageway | 22 |
| Underground passages | 20 |
| Underground passage | 19 |
| Underground party | 17 |
| Underground part of a plant | 27 |
| Underground part | 16 |
| Underground org.? | 17 |
| Underground org. | 16 |
| Underground network | 19 |
| Underground nesters | 19 |
| Underground music genre | 23 |
| Underground movement leader? | 28 |
| Underground molten rock | 23 |
| Underground missile site | 24 |
| Underground missile launch site | 31 |
| Underground meeting place | 25 |
| Underground mammal | 18 |
| Underground mag of the 1960s | 28 |
| Underground lines | 17 |
| Underground letters | 19 |
| Underground layer | 17 |
| Underground lava | 16 |
| Underground launch site | 23 |
| Underground Kentucky attraction | 31 |
| Underground installation | 24 |
| Underground infiltrator | 23 |
| Underground home | 16 |
| Underground hollow | 18 |
| Underground hip-hop release | 27 |
| Underground grp. | 16 |
| Underground growths | 19 |
| Underground growth | 18 |
| Underground group | 17 |
| Underground gate | 16 |
| Underground folklore creature | 29 |
| Underground floor | 17 |
| Underground find | 16 |
| Underground film actress Sedgwick | 33 |
| Underground figure? | 19 |
| Underground figure | 18 |
| Underground facility | 20 |
| Underground explosions | 22 |
| Underground explosion | 21 |
| Underground explorer | 20 |
| Underground experiment, for short | 33 |
| Underground experiment, briefly | 31 |
| Underground event | 17 |
| Underground entrance | 20 |
| Underground edibles | 19 |
| Underground drain | 17 |
| Underground discovery | 21 |
| Underground discoveries | 23 |
| Underground deposits | 20 |
| Underground deposit | 19 |
| Underground dance party | 23 |
| Underground crop storage area | 29 |