I have Honeywell TRVs, > 20 years old. They're provided with isolating caps. You remove the TRV head, screw on the cap and it closes the plunger. I assume that gives complete closure, like an iso valve, but it's many years since I tried it. Whether more modern ones have this feature, or whether yours does, I don't know.
But unless you can catch the water effectively, or there's nothing it can damage, you might be better off isolating all the other rads then draining the system remotely. That way there's only a small amount of water left in the rad. Also it's easier to catch the water from a drain fitting, so if you have inhibitor in the system you can return it when the job's done.
