| 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 |
| Underground creature | 20 |
| Underground conduits for water | 30 |
| Underground conduits | 20 |
| Underground conduit | 19 |
| Underground complexes | 21 |
| Underground commuter | 20 |
| Underground colonist | 20 |
| Underground coal source | 23 |
| Underground channel | 19 |
| Underground chambers | 20 |
| Underground chamber | 19 |
| Underground cemetery | 20 |
| Underground cartoonist's products | 37 |
| Underground car | 15 |
| Underground burrower | 20 |
| Underground burial site | 23 |
| Underground burial places | 25 |
| Underground bud | 15 |
| Underground branch | 18 |
| Underground blast, perh. | 24 |
| Underground band? | 17 |
| Underground band | 16 |
| Underground asset | 17 |
| Underground artists, maybe | 26 |
| Underground art site in Spain | 29 |
| Underground anchors | 19 |
| Underground activity | 20 |
| Underground | 11 |
| Undergraduate law deg. | 22 |
| Undergraduate degs. | 19 |
| Undergraduate degree, to a pilot | 32 |
| Undergrads: Abbr. | 17 |
| Undergrads' Greek leadership society | 40 |
| Undergrads' degrees | 23 |
| Undergrads | 10 |
| Undergrad. degrees | 18 |
| Undergrad. bigwigs | 18 |
| Undergrad, perhaps | 18 |
| Undergrad's digs | 20 |
| Undergrad's bugbear | 23 |
| Undergrad tech degs. | 20 |
| Undergrad pad | 13 |
| Undergrad MIT degrees | 21 |
| Undergrad housing | 17 |
| Undergrad degs. | 15 |