ALDA Loose

The ALDA on my pump has always been a little loose. Today I noticed a very slight oil leak from under the big nut where it goes into the top of the injection pump. I can't tell if this nut is part of the ALDA, or is for keeping things tight. Car is runnng fine,just need to know how to tighten this up to stop the leak. Don't want to force anything and no mention of this in the search.
On another note I ordered all the lower wear parts minus ball joints for the front suspension. (always something, but beats car payments) today from fastlane. Under $130.00 including 2nd day shipping. Alignment shop wanted $235.00 for the same parts. Got to get her ready for the upcoming summer road trips to backpack GA, Ten, Ky.