Almost set one, maybe two bones? (5)
I believe the answer is:
radii
'maybe two bones?' is the definition.
(plural of radius)
'almost set one' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'set' becomes 'radio' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'radio' with its final letter taken off is 'radi'.
'radi'+'i'='RADII'
(Other definitions for radii that I've seen before include "spoke with others" , "Halves of diameter" , "Spokes of a circle" , "Straight lines from the centre to the surface of a sphere" , "Lines from a circle's centre to the circumference" .)