Bone slightly raised, covering one (5)
I believe the answer is:
tibia
'bone' is the definition.
(tibia is a kind of bone)
'slightly raised covering one' is the wordplay.
'slightly' becomes 'abit' (I've seen this before).
'raised' shows that the letters should be reversed in order.
'covering' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'abit' reversed gives 'tiba'.
'tiba' going around 'i' is 'TIBIA'.
(Other definitions for tibia that I've seen before include "The large shinbone" , "The formal shinbone" , "ancient pipe" , "Part of leg of" , "part of skeleton" .)