Part fashionably black, bright outside (4,4)

I believe the answer is:

shin bone

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Another definition for shin bone that I've seen is " Tibia".)

I've seen this clue in The Hindu.

Want a hint initially instead of a full solution? Install my app