Just to clarify, you want to be able to upload an audio file and click on it during a meeting/webinar so all attendees can hear it. If this is correct, the only way to play an audio file would be to share it. This would mean you would have to have an audio player on your computer, click on share, select that app and then play the audio file. This would be disruptive during the meeting so probably not what you want.
An option would be to have an audio player near your computer with the applause sound queued up and play it so your microphone picks it up. You will need to make sure you have "music mode" enabled for your audio or the Noise Removal setting will cancel it out.
There is a product enhancement request that shows it's being planned for a future release that may end up giving you what you need. Here's a link to the request. If you think it would give the functionality you're looking for, you can vote for it to show your support. If you need something different, you can also create your own product enhancement request.
https://ciscoccp.ideas.aha.io/ideas/WXCUST-I-1480
Good luck.
