Bone (5)
'bone' is the definition.
(rib is a type of bone)
This is the entire clue.
(Other definitions for rib that I've seen before include "joke" , "One of 12 pairs of curved bones" , "spare one?" , "One of the 12 pairs in the body" , "Tease; pectoral bone" .)
'bone' is the definition.
(I know that femur is a bone)
This is all the clue.
(Other definitions for femur that I've seen before include "Thigh bone" , "Thighbone" , "Longest bone in the human body" , "Bone in leg" , "Part of leg" .)