Not talking about abandoning book is slander! (3)
I believe the answer is:
mud
'is slander' is the definition.
(as in to drag someone's name through the mud)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for mud that I've seen before include "Offensive remarks" , "Water-soaked soil" , "Mire" , "Earth and water mixed" , "Clay" .)