What does the cryptic crossword clue "Move around the Tube, essentially underground in America (6)" mean?

The wordplay uses a container (one word inside another). UB (synonym="UB") in SWAY (synonym="move") = SUBWAY The answer is SUBWAY.

Move around the Tube, essentially underground in America (6)

Guardian Cryptic #29101 | 3 Down | 2023-06-20 flower