The most common and most likely answer to this crossword clue is the 5 letter word CALVE
I've seen this crossword clue in Financial Times
C
A
L
V
E
More clues leading to the result CALVE
- Drop a little lower, keeping length in mind
- Local vet’s helping cows do it
- Left in hollow to give birth
- In Antarctica, separate line found in hollow space
- Drop medical vehicle’s display
- Length in chamber needed to produce young
- Produce new animal and slice it up, say
- Left in chamber to produce young whales
- Typical vegetarians keeping produce young
- Deliver brief US state victory over East
Buddy explains!

The straight part
We know that "cows do it" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cows do it = calve.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 CALVE mean?
CALVE verb- To give birth to a calf
- To assist in a cow's giving birth to a calf
- To give birth to (a calf)
- (especially of an ice shelf, a glacier, an ice sheet, or even an iceberg) to shed a large piece, e.g. an iceberg or a smaller block of ice (coming off an iceberg)
- (especially of an iceberg) to break off
- (especially of an ice shelf, a glacier, an ice sheet, or even an iceberg) to shed (a large piece, e.g. an iceberg); to set loose (a mass of ice), e.g. a block of ice (coming off an iceberg)