Sap in cedar essentially drops (5)
I believe the answer is:
drain
'sap' is the definition.
(synonyms)
'cedar essentially drops' is the wordplay.
'essentially' indicates the central letters.
'drops' becomes 'rain' (drops of water).
The centre of 'cedar' is 'd'.
'd'+'rain'='DRAIN'
'in' is the link.
(Other definitions for drain that I've seen before include "Deprive gradually of strength or resources" , "See 11 dn" , "Draw off U sewer" , "Something using up resources" , "Culvert" .)