Great quantity left out of garden material (4)

I believe the answer is:

much

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'great quantity' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for much that I've seen before include "A lot of unnecessary fuss" , "A large amount" , "Chum (anag.)" , "Great quantity" , "Plenty" .)

I've seen this clue in The Times.

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