What does the cryptic crossword clue "Worried choir rang agent to obtain church music (9,5)" mean?

The wordplay uses an anagram. anagram of CHOIR + RANG + AGENT = GREGORIANCHANT The answer is GREGORIANCHANT.

Worried choir rang agent to obtain church music (9,5)

Daily Mail Cryptic #16413 | 26 Across | 2020-09-29 flower