Greasy plate’s protection not initially required (4)
I believe the answer is:
oily
'greasy' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
(Other definitions for oily that I've seen before include "Like a lot of fish" , "Greasy - obsequious" , "Smooth; like lubricant" , "Covered in lubricant" , "Smarmy" .)