Bone that always has one end in the centre (6)

I believe the answer is:

radius

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'bone' is the definition.
(I know that radius is a bone)

I can't explain the remainder of the clue.

(Other definitions for radius that I've seen before include "Centre-circumference length" , "Straight line from circle's centre to circumference" , "from centre to boundary" , "It runs from the centre to the circumference" , "Wine; burial places" .)

I've seen this clue in The Times.

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