The most common and most likely answer to this crossword clue is the 6 letter word GARGLE
I've seen this crossword clue in The Times
G
A
R
G
L
E
Buddy explains!
The straight part
We know that "Swill" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swill = gargle.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 GARGLE mean?
GARGLE noun- A liquid used for gargling
- The sound of gargling
- Lager, drink
- To clean one's mouth by holding water or some other liquid in the back of the mouth and blowing air out from the lungs
- To make a sound like the one made while gargling
- To clean a specific part of the body by gargling (almost always throat or mouth)
- To use (a liquid) for purposes of cleaning one's mouth or throat by gargling.
- A carved grotesque figure on a spout which conveys water away from the gutters.
- Any decorative carved grotesque figure on a building.
- A fictional winged monster.
- An ugly woman.