Answer: monitoring

AnswerCrossword Clue
MONITORINGListening in
monitoringListen to and report on (a foreign radio broadcast or a telephone conversation)
monitoringMaintain regular surveillance over
monitoringObserve and check the progress or quality of (something) over a period of time; keep under systematic review
monitoringCheck or regulate the technical quality of (a radio transmission or television signal)
monitoringthe act of keeping track of