The most common and most likely answer to this crossword clue is the 7 letter word INSTEPS
I've seen this crossword clue in The Sunday Telegraph
I
N
S
T
E
P
S
Buddy explains!

The straight part
We know that "Parts of feet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case parts of feet = insteps.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 INSTEPS mean?
INSTEPS noun- The arched part of the top of the foot between the toes and the ankle.
- A section of any footwear covering that part of the foot.
- In horses, the hind leg from the ham to the pastern joint.