Not sure at all!
But do you need to?
That's essentially just the main axis or guide rod for the pistol grip, it doesn't do anything but keep everything aligned (does it?).
I had a look at mine earlier, & there's no obvious screw threads etc - maybe you'd see how its attached to the action when you dis-assemble the action block ?
It's a shame your photo has the Mag lock in the open position as it gives the impression that the 'silver' rod is clamped by the grip hex bolt (at top) whereas that is really gripping the larger 'brass' rod - The Bolt in fact. What your pics does show well is the Bolt lug within the action that the sidelever works upon (just sitting there waiting

).