How to fix sticky lifter.

I would remove it and inspect the lifter. If the lifter is cupped on the bottom you will have to replace the cam and all the lifters. Can you isolate which lifter it is? If you can I have removed and swapped lifters through the valve cover with a strong magnet. Best is to remove the intake manifold. Also check for bent push rods. I have seen one that worked fine but had a couple tweaked pushrods that made a lifter type noise. Also and lastly I have seen on several occasions where a lifter noise was actually something more serious. I had a 273 that was rebuilt and always had a. Slight lifter tap. I adjusted the lifters constantly sometimes it was there some times it was gone. Oil pressure was perfect. Idled at 40 60 to 70 warm and driving down the road. That tap slowly got louder over the next year until a rod came out the side. Was quiet then.