The Clear Field Value post function clears any defined field after a transition has been completed. This can be a system or a custom field. The field can be on the issue in transition(within the same issue) or on a related issue, like a sub-task, a linked issue, or an issue within an Epic (during the transition on the Epic). For example, if an issue is moved to re-open, you might want to clear the fix version or due date so new values can be entered.
You can add any number of fields to perform the clear operation. Click the Add + button to add additional fields to your configuration.