Flowerbed matter (4)

I believe the answer is:

soil

(Other definitions for soil that I've seen before include "Top layer of the surface of the earth" , "Loose upper layer of earth" , "In which plants grow" , "refuse" , "Earth; make dirty" .)

I've seen this clue in The Mirror.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.