Milk type (4)
I believe the answer is:
skim
'milk type' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for skim that I've seen before include "Remove top (of milk)" , "avoid paying income tax" , "Remove surface layer" , "Glide smoothly over" , "Remove (or move close to) liquid surface" .)