Need to find out to how to clean gel ink pen off an oil painting. It has been varnished. Tried cleaner.?

If the gel ink pen is under the varnish there really isn't a way to remove it. If the pen is on top of the varnish, you could use a bit of diluted turpentine or mineral spirits to gently remove the varnish in that portion of the painting, if the varnish is suitable for removal (not all varnish is). You have to be extremely careful not to get the turpentine on the paint because it will lift the paint as well.