What does the cryptic crossword clue "Pick up heavy breathing on microphone, that’s shocking (7)" mean?

The definition is "shocking". The wordplay uses a homophone (sounds like). Homophone of “sighs” + MIC The answer is SEISMIC.

Pick up heavy breathing on microphone, that’s shocking (7)

Guardian Cryptic #29113 | 19 Down | 2023-07-04 flower