You can create a clip before you are ready to upload an audio file.

First, go to the Clips page in the Program you're looking to create a draft clip for. 

Hit the options arrow beside 'Upload audio files'.

Then you can name the clip, add a description, and configure the clip as normal. 

At any point you can upload audio to the clip, by hitting Upload audio. 

At this point you can click save and then come back at any time to upload your audio, and find your draft in the clips window. 

When you're ready to upload the audio, you have the option of importing the mp3 metadata including the title, artwork and even chapter markers. 

Just check the box for the elements of the mp3 metadata that you'd like to import.

Once the clip is uploaded, click save and you're ready to publish to your RSS feed or share on social media!