Boat steerer loses its first milk provider (5)
I believe the answer is:
udder
'milk provider' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for udder that I've seen before include "Animal mammary gland" , "Animal organ with more than one teat" , "milk supplier" , "Milk supply" , "Bovine mammary gland" .)