The graphics hint that this puzzle is a connecting wall from the gameshow Only Connect.
Sorting the clues into four groups of four, we get:
| Group | Connection | |||
|---|---|---|---|---|
| Knob | Edgework | Tetris | Math | NEEDY |
| Err is human | a T | Boldly Go | Be | TO |
| U | the Key | Right-Hand | Down for What | TURN |
| Cloudy | Shady | Misty | Somber | DARK |
This forms the clue phrase NEEDY TO TURN DARK, the solution to which is
LIGHTS OUT