Fermentation sediment (4)
I believe the answer is:
lees
'fermentation sediment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lees that I've seen before include "Sediment that settles at the bottom of wine" , "worst part" , "Grounds" , "Sediment from fermentation of alcohol" , "Knock back these dregs of liquor" .)