[Seahawk]

The post isn't holding up the tree, the lower, large trunk-like branch is...I bet it is embedded six inches deep in the ground. That tree weights many, many tons.

I'd get a good pole saw and and trim right to left, get the weight off as Burnin' Oil mentioned. Before you do anything, however, clean the little stuff first and make sure you get all the crap around the tree cleared. I always want a clear path to scoot, exercising the better part of valor.

You'll know a lot more on how best to attack the big stuff after that. My bet is that trimming off the top large branch first, leaving the lower section to support while you cut, will work best.

I've had to deal with two Oaks that fell on my farm. Get the weight off.