The most common and most likely answer to this crossword clue is the 10 letter word HANDSPRING
I've seen this crossword clue in The Sunday Telegraph
H
A
N
D
S
P
R
I
N
G
Buddy explains!

The straight part
We know that "gymnastic feat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gymnastic feat = handspring.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 HANDSPRING mean?
HANDSPRING noun- A somersault made with the assistance of the hands placed upon the ground.