The most common and most likely answer to this crossword clue is the 10 letter word LIMONCELLO
I've seen this crossword clue in The Guardian
L
I
M
O
N
C
E
L
L
O
More clues leading to the result LIMONCELLO
Buddy explains!

The straight part
We know that "Liqueur" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case liqueur = limoncello.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 LIMONCELLO mean?
LIMONCELLO noun- A kind of Italian lemon-flavoured liqueur.
- A glass of such drink.