Spokes in bones (5)
I believe the answer is:
radii
I believe this is a double definition.
'spokes' is the first definition.
('radius' can be a synonym of 'spoke')
'bones' is the second definition.
(radius is a kind of bone)
'in' is the link.
(Other definitions for radii that I've seen before include "They meet in the middle of a circle" , "Lines from a circle's centre to the circumference" , "spoke with others" , "Straight lines from centre of a circle" , "Half-diameters" .)