Crux of a matter (3)
I believe the answer is:
nub
(Other definitions for nub that I've seen before include "Centre, heart" , "Most essential part of an idea" , "Crux, central point" , "Core, pith or gist" , "Crux (of a matter)" .)
I believe the answer is:
nub
(Other definitions for nub that I've seen before include "Centre, heart" , "Most essential part of an idea" , "Crux, central point" , "Core, pith or gist" , "Crux (of a matter)" .)