Source of milk (4)
'source of milk' is the definition.
(eg a cow's udder)
This is all the clue.
(Other definitions for udder that I've seen before include "Animal mammary gland" , "Animal organ with more than one teat" , "Milk supply" , "Cow's teat" , "Mammary gland of cow" .)
'source of milk' is the definition.
(body part which dispenses milk)
This is the entire clue.
(Other definitions for teat that I've seen before include "Part of feeding bottle" , "Nipple or dug" , "Bulb on infant's bottle" , "essential for babies" , "Piece on baby's bottle" .)