What does the cryptic crossword clue "Amount of liquid in pail I trebled (5)" mean?

The definition is "Amount of liquid". The wordplay uses a hidden word. Hidden in "amount of liquid in paiL I TREbled" The answer is Litre.

Amount of liquid in pail I trebled (5)

Telegraph Prize Cryptic #3001 | 10 Across | 2019-04-28 flower