The most common and most likely answer to this crossword clue is the 6 letter word POTEEN
I've seen this crossword clue in The Daily Telegraph
P
O
T
E
E
N
Buddy explains!
The straight part
We know that "It’s still produced in Ireland, though illegally" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s still produced in ireland, though illegally = poteen.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 POTEEN mean?
POTEEN noun- Illegally produced Irish whiskey; moonshine.
- (by extension) An unlicensed drinking establishment selling illegally produced Irish whiskey.