Report scale and method as liquid strained (4)
I believe the answer is:
Here is my best explanation:
'liquid strained' is the definition.
I cannot understand how the remainder of the clue works.
(Other definitions for whey that I've seen before include "Curds and - -", "Watery constituent of milk", "Separated part of milk", "Milk serum", "Product of clotting milk", "Watery liquid left when milk forms curds", "Residual liquid from clotted milk", "Residue from junket", "Milk component" and "Watery remains after the curds are separated in milk".)