What does the cryptic crossword clue "… a lot of trees waste away going to pot (7)" mean?

The wordplay uses a charade (building blocks). PINE (synonym="(to") + TUM (synonym="=pot(-belly") = PINETUM The answer is PINETUM.

… a lot of trees waste away going to pot (7)

Independent Cryptic #11720 | 9 Across | 2024-05-03 flower