You can restore a single app, or a single app's data, using Titanium. But if you want to restore say a single podcast without overwriting others then you can't use the app for that.
But I'd have thought that podcasts would be big enough that they'd be written to sd (real or "internal" ) somewhere. If so I'd not expect Ti to back them up, so it's worth making sure they aren't hidden somewhere on sd (in an obscurely named folder or in a subfolder).
If they are in /data/data then you should be able to manually extract them from the Ti backup. If you look in the Titanium folder on your sd card you'll see the format: data for each app are stored as gzipped archives (.tar.gz) of the corresponding folder in /data/data. Of course it depends how the podcast app works - if it keeps a database of what podcasts it has then you may be able to copy the audio file (from wherever it is) but it may be harder to tell the podcast app it's there without restoring the corresponding copy of the database (overwriting any newer one). Just speculating though, as I don't know the app.