Q: Purchased a song in iTunes a week ago with visa card and it's still pending

As well as receiving an emailed receipt from iTunes (is that what you mean by 'some type of email authorisation' ?) it should show on your account's purchase history : See your purchase history in the iTunes Store on a Mac or PC - Apple Support

Or if iTunes wasn't able to successfully collect the money from your card it should show as owing : Pay an unpaid balance in the iTunes Store - Apple Support - does anything show there ? If not then it implies that it's gone through successfully, but credit card purchases can sometimes take a while

10 days have passed and my Visa statement on line still has $1 stuck in it and still  pending is that the reason I cannot put that song on my iPod.

No, the $1 is a temporary store holding charge which your card issuer should have automatically removed (most card issuers only take a few days) - that will have no affect on whether you can sync songs to a device.

I did not receive a email like that

What email haven't you received ? The only emails that iTunes sends are purchase receipts and when you change something on your account (e.g. password, payment details) - you won't get an email about owing iTunes, if that is what you are referring to, that only shows on an account

When syncing you have the song selected for syncing ? And you've tried de-selecting it, syncing, and then reselecting and resynning ?

For the charge, if you log into your account are there any errors showing on the payment details screen ? Though you've received the emailed receipt it doesn't necessarily mean that the purchase has gone through successfully, iTunes may not have been able to collect the money from the card (in which case an error should show on the payment details screen on your account on your computer's iTunes)