Greasier (6)
I believe the answer is:
oilier
'greasier' is the definition.
('oily' can be a synonym of 'greasy')
This is all the clue.
(Other definitions for oilier that I've seen before include "More lubricated or flattering" , "More greasy or unctuous" , "rather greasy" , "More viscous or unpleasantly smooth" , "having applied more sun cream?" .)