Radio/clockloses power when I plug in the lighter

There really isn't such a thing as a generic fuse. The only concern is that you put the correct value back in. First I'd suspect there's a problem with the lighter socket. Sometimes accessories such as cell phone chargers have a plug that isn't exactly compatible with lighter sockets and they can touch multiple points and create a short. They usually will work if you plug it in rotated the right way. I would look closer at the new fuse to be sure it's plugged in securely and there's no corrosion on the terminals. If the new fuse isn't blowing when the radio quits, it suggests there's too much resistance in the circuit. That will have the greatest affect when more current is demanded such as when plugging in the lighter. The radio memory circuit and clock by themselves take very little current so that suspect resistance won't be a problem when nothing else is turned on.

If you don't see anything obvious with that new fuse, plug the lighter in so the problem occurs, then measure the voltage right at the fuse. There's two small holes on top to stick the voltmeter probe. If you find a different voltage on each side of the fuse, it's just barely blown but left a carbon track behind. That is fairly rare but can pass enough current for the radio and clock.

Nope. Basically, a fuse is a fuse. I think if you monkey with the Ipod plug and rotate it, you will reach a point where something touches and the fuse blows. When that happens to me, I just watch the orientation closely when I plug it in, and I make sure to always have it oriented the same way.