Fix in place a character's node?

Mouser

I will attempt to expand and explain more clearly my above jibberish.

I am animating a walk cycle (in place) a horse character 
(https://www.daz3d.com/toon-horse-for-daz-horse-3)
and I want to keep (possibly) the lowest neck node static to keep the head roughly steady as it end up all over the place.

Has anyone any suggestions for a solution?
Thanks
DJM