The most common and most likely answer to this crossword clue is the 4 letter word KEGS
I've seen this crossword clue in The Guardian
K
E
G
S
More clues leading to the result KEGS
Buddy explains!
The straight part
We know that "Whence we get beer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case whence we get beer = kegs.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 KEGS mean?
KEGS noun- A round, traditionally wooden container of lesser capacity than a barrel, often used to store beer.
- Underpants.
- Trousers (pants).