Question importing English dairy product (4)
I believe the answer is:
whey
'dairy product' is the definition.
(whey is a kind of dairy product)
'question importing english' is the wordplay.
'question' becomes 'why' (why is a question word).
'importing' indicates putting letters inside.
'english' becomes 'E' (abbreviation).
'why' enclosing 'e' is 'WHEY'.
(Other definitions for whey that I've seen before include "Watery constituent of milk" , "Watery part of milk after curd separation" , "Watery dairy product" , "Water separated from milk" , "Part of Miss Muffet's diet" .)