Lubricate (3)
'lubricate' is the definition.
(synonyms)
This is all the clue.
(Other definitions for oil that I've seen before include "eg Olive" , "Fluid lubricant" , "Viscous substance as lubricant" , "Fuel, lubricant" , "SECOND PART OF 23" .)
'lubricate' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for grease that I've seen before include "Possible cause of slip-up" , "Musical that sounds like a country" , "Lubricate (-ant)" , "Travolta's 1978 film" , "A thick oily substance" .)