What cow chews is about right for dairy product (4)
I believe the answer is:
curd
'for dairy product' is the definition.
(curd is a kind of dairy product)
'what cow chews is about right' is the wordplay.
'what cow chews' becomes 'cud' (cud is regurgitated food chewed by cows).
'is about' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'cud' going around 'r' is 'CURD'.
(Other definitions for curd that I've seen before include "Part of milk" , "Coagulated milk, used to make cheese" , "Basis for cheese" , "It's used in making cheese" , "Fatty stuff" .)