What does the cryptic crossword clue "Drink locked up by Cinderella's sisters (5)" mean?

The definition is "Drink". The wordplay uses a hidden word. Hidden in "drink locked up by cinderelLA'S SIsters" The answer is LASSI.

Drink locked up by Cinderella's sisters (5)

Independent Cryptic #1817 | 4 Down | 2024-12-22 flower