If it is recessed things get difficult.
I'm guessing you lost a heater lead. If it was not a heater lead you could probably use conductive glue, but the heater draws a lot of current and odds are conductive glue won't survive that...
If the glass is reasonably thick around the lead and there's a raised bit of glass wrapped around the lead stub then you may be able to expose a solder able nub by grinding the glass down with a small gentle dremmel grinding bit.... but grind too far and you loose vacuum. Also you have to apply heat with the soldering iron for the shortest possible time needed to get a solder joint....too long heating it and the glass will crack and the vacuum will leak... grinding the glass will also make it more prone to cracking.......
What you have is a game of finesse, speed, judgement and luck with the future of your CRT on the line....No pressure.
