The most common and most likely answer to this crossword clue is the 4 letter word ULNA
I've seen this crossword clue in Independent
U
L
N
A
More clues leading to the result ULNA
- Careful, naturally, to bury this bone
- Bone discovered up in San Luis
- Stubbs preserved large bone from horse’s leg
- Some fanciful name for part of the arm
- Stubbs captures left part of horse’s forelimb
- Children leaving a lunch played around with part of chicken wing?
- Bashful naturist covers up part of anatomy
- Part of the arm that is somewhat painful, naturally
- Girl covering bit of leg with part of arm
- Arm section to infiltrate all-powerful nation
Buddy explains!

The straight part
We know that "part of anatomy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of anatomy = ulna.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 ULNA mean?
ULNA noun- The bone of the forearm that extends from the elbow to the wrist on the side opposite to the thumb, corresponding to the fibula of the hind limb. Also, the corresponding bone in the forelimb of any vertebrate.