Ring the film centre for something smooth (3)
I believe the answer is:
oil
'smooth' is the definition.
(to oil or grease something is to smooth it)
'ring the film centre' is the wordplay.
'ring' becomes 'O' (letter resembling a ring).
'centre' means to look at the middle letters.
The middle letters of 'film' are 'il'.
'o'+'il'='OIL'
'for something' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for oil that I've seen before include "What can be extracted" , "eg Olive" , "Slippery liquid" , "Viscous substance for lubrication" , "Lubricate; fuel" .)