Grease-filled (4)
I believe the answer is:
oily
'grease-filled' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oily that I've seen before include "Unpleasantly ingratiating" , "Smooth; like lubricant" , "Oleaginous" , "Like a lot of fish" , "Greasy - obsequious" .)