Oil the wood (5)
I believe the answer is:
olive
This clue is a double definition.
'oil' is the first definition.
(as in olive oil)
'wood' is the second definition.
(olive is a kind of wood)
'the' is the link.
(Other definitions for olive that I've seen before include "Fruit; Popeye's girlfriend" , "Girl's name - colour" , "Mediterranean tree-fruit - nice in martini" , "Small green Mediterranean tree-fruit (5)" , "girl" .)