The action to Delete Files will let you delete attached the files attached to items Podio.
This action can be used in a For Each to delete files in multiple items.
WARNING: This action is irreversible - be sure that the correct file is being deleted before running the flow.
For example, if you want to have a flow that creates a PDF and attaches to an item, Workflow Automation won't replace the existing file with the same file name. It will simply attach the PDF without removing any existing files. With Delete Files, you can avoid having a long list of PDF files with the same file name.
Start the flow by selecting the Trigger and add any Filters required.
Next, select the Delete File(s) from the sidebar under Actions.
First, select the files you want to delete. Choosing the Most Recent One will delete the most recent file that Workflow Automations can find attached to the item. Choosing All Files will delete all files that Workflow Automations finds on an item.
With Pattern allow you to specify certain files to delete with a particular filename. It is important to note that any pattern should be placed between the two *.
For example, if you wanted to delete all the files that had a particular filename of "invoice", you would need to enter into the pattern input box, invoice. 
Add in other Actions to complete or just finish and Save the flow.