Sediment in bottle, essentially (4)
I believe the answer is:
lees
'sediment' is the definition.
(I've seen this before)
'in bottle essentially' is the wordplay.
'in' indicates the answer is hidden within the clue.
'LEES' is hidden within 'bottle essentially'.
(Other definitions for lees that I've seen before include "Sediment that settles at the bottom of wine" , "Eels found in sediment" , "Grounds" , "Sediement or else" , "Dregs of drink" .)