The most common and most likely answer to this crossword clue is the 6 letter word TIBIAS
I've seen this crossword clue in Financial Times
T
I
B
I
A
S
Buddy explains!

The straight part
We know that "bones" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bones = tibias.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TIBIAS mean?
TIBIAS noun- The inner and usually the larger of the two bones of the leg or hind limb below the knee, the shinbone
- The second segment from the end of an insect's leg, between the femur and tarsus.
- The third segment from the end of an arachnid's leg, between the patella and metatarsus.
- A musical instrument of the flute kind, originally made of the leg bone of an animal.