Quick to ditch ultimate dairy product (4)

I believe the answer is:

brie

I'm a little stuck... Click here to teach me more about this clue!

'dairy product' is the definition.
(I know that Brie is a type of cheese)

I don't understand the rest of the clue.

(Other definitions for brie that I've seen before include "dairy product" , "Food" , "French cream cheese" , "Prov. squalid place" , "French 8 across" .)

I've seen this clue in The Sun.

Want a hint initially instead of a full solution? Install my app