It is not possible to clear Alarm with the Streaming Analytics only with EPL. But there is not an easy way to clear some Alarms if they have reached a specific time or so on. Alarms could only be created but to clear Alarm there are no easy possibilities.
The ability clear an alarm from Analytics Builder was added in 10.9 (Jul 2021).
https://cumulocity.com/releasenotes/release-10-9-0/streaming-analytics-10-9-0/#10_9_0
You could use this with a Cron block to wait a specified time after an alarm was first created. Did you need more than this? If so, could you provide a few more details? Thanks.