What does the cryptic crossword clue "Great hopes Berg cultivated about a stage work (3,7,5)" mean?

The wordplay uses an anagram. anagram of GREAT + HOPES + BERG + A = THE BEGGARS OPERA The answer is THE BEGGARS OPERA.

What is the answer to "Great hopes Berg cultivated about a stage work (3,7,5)"?

The answer is THE BEGGARS OPERA.

Times Cryptic #27874 | 26 Across | 2021-01-14 flower