Jasmine:

I'm presuming that this is a Whirlpool dryer cuz I know Whirlpool uses a felt seal at the back of the dryer drum.

The proper repair would be to replace the sealing felt at the back of the dryer drum.

You see, the dryer drum rolls on rollers and there's a felt "skirt" at the back of the drum that forms a seal around the drum to prevent that warm moist air from blowing out at the back of the drum. When that seal gets worn out, the warm moist air inside the dryer blows onto the polished steel that the felt seal has been rubbing against for the last two decades and causes it to rust.

Clothes that get between the dryer drum and that now rusting polished steel end up with rust marks on them.

So, the correct fix is to take the drum out of the machine, remove the old felt seal and install a new one. I've done this on my sister's Whirlpool dryer (sold under the brand name "Inglis" here in Canada), and it's not all that hard to do, but you will need several volunteers (pronounced "friends" or "family members") to help you put the new seal on straight.

Every appliance manufacturer has their own recommended adhesive to put the new seal on, and it's probably best to use the factory recommended product. If it's no longer available, phone the Whirlpool factory authorized service depot in your area and ask what they use. This is a problem that happens with every Whirlpool/Inglis dryer eventually.