Bovine mammary glands (6)
I believe the answer is:
udders
'bovine mammary glands' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for udders that I've seen before include "de rest" , "Cows' teats" , "Mammary glands of cows" , "Teats of a cow" , "Milk producers" .)