Clear
This action empties the binary to send and sets its size to 0.
If you have the Automatically clear binary property checked, then effectively this action will occur whenever you send/blast a binary message, after the transmission. Otherwise, it is up to you to decide when to clear a binary message.
For advanced users: If you want to reuse multiple messages, consider using the Binary Object and using the Binary to send > Add binary action instead. For more, read the MMO merge tip in the Tips topic.