What does the cryptic crossword clue "1,099 probed by us – sound? (5)" mean?

The wordplay uses a container (one word inside another). US (synonym="US") in MIC (synonym="MIC") = MUSIC The answer is MUSIC.

1,099 probed by us – sound? (5)

Guardian Cryptic #29615 | 24 Down | 2025-02-11 flower