Surrounding region of a bone (6)
I believe the answer is:
radius
This clue could be a double definition.
'surrounding region' is the first definition.
'radius' can be an answer for 'region' (radius is a kind of region). I am not sure about the 'surrounding' bit.
'a bone' is the second definition.
(radius is a kind of bone)
'of' is the link.
Can you help me to learn more?
(Other definitions for radius that I've seen before include "Bone of forearm - distance from centre" , "Half a circle's diameter" , "from centre to boundary" , "It runs from the centre to the circumference" , "Line from centre to edge of a circle" .)