Leaky Basket Strainer/Frozen retaining nut

I need some advice on removing a frozen basket strainer nut, so I can reseal the basket strainer with plumber's putty. When I try to turn the nut in either direction the whole basket strainer turns. I've tried wedging a screwdriver in the bottom part of the basket strainer to keep it from moving, but it didn't work--and it started to bend the metal. If that bottom part of the strainer breaks, then there's nothing left to grab onto.

Would a torch help? Do I need to cut the nut out?

Thanks,
Eric

You can cut it with a hacksaw, then remove it. I would just replace the old one with a new one. Don't try and reuse it.

drain

Cut it out and replace it.

I was able to cut it out in less than a minute with my dremel!

Thanks for the advice.

Eric