The most common and most likely answer to this crossword clue is the 6 letter word FEMORA
I've seen this crossword clue in Financial Times
F
E
M
O
R
A
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 = femora.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 FEMORA mean?
FEMORA noun- A thighbone.
- The middle segment of the leg of an insect, between the trochanter and the tibia.
- A segment of the leg of an arachnid.