The most common and most likely answer to this crossword clue is the 8 letter word HOLSTEIN
I've seen this crossword clue in The Guardian
H
O
L
S
T
E
I
N
More clues leading to the result HOLSTEIN
- The Lions' fresh source of milk?
- Type of cattle break metal fences close to byre
- Composer on vessel, heading off for German region
- Composer oddly overlooked Delian cow
- Composer with one German cow
- Bar manager meets a German milk supplier
- Place for a gun mostly in part of Germany
- Cheap accommodation lets student travel west in German region
- Dairy cow’s gun holder striking back hip
Buddy explains!

The straight part
We know that "cow/cow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cow/cow = holstein.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does HOLSTEIN mean?
HOLSTEIN noun- A type of dairy cattle, distinctively colored in splotches of black and white.
- A breed of horse, thought to be the oldest of the warmblood breeds, used in show jumping.