What does the cryptic crossword clue "Drink in Wetherspoons, for example, 20% off (4)" mean?

The definition is "Drink". The wordplay uses a deletion. CHAI (deletion) = CHAI; definition: "Drink" The answer is CHAI.

Drink in Wetherspoons, for example, 20% off (4)

Guardian Cryptic #29042 | 12 Across | 2023-04-12 flower