Drink knocked back before working is a spirit (6)
I believe the answer is:
daemon
'spirit' is the definition.
(I know that daemon is a type of evil spirit)
'drink knocked back before working' is the wordplay.
'drink' becomes 'mead' (mead is a kind of drink).
'knocked back' is a reversal indicator.
'before' is a charade indicator (letters next to each other).
'working' becomes 'on' (on can mean working or activated).
'mead' reversed gives 'daem'.
'daem'+'on'='DAEMON'
'is a' is the link.
(Other definitions for daemon that I've seen before include "Evil spirit" , "guardian spirit" , "Spirit in ancient Greek belief" .)