A little oregano in the oil (6)
I believe the answer is:
anoint
'oil' is the definition.
(synonyms)
'a little oregano in the' is the wordplay.
'a little' indicates the answer is hidden within the clue (a little bit of the clue).
'ANOINT' can be found hidden inside 'oregano in the'.
(Other definitions for anoint that I've seen before include "Administer sacred oils as to the sick" , "Consecrate with blessed oils" , "Bless with holy oil" , "Choose as successor" , "Put in position of authority" .)