The most common and most likely answer to this crossword clue is the 6 letter word RUSTY*
I've seen this crossword clue in The Guardian
R
U
S
T
Y
*
Buddy explains!
The straight part
We know that "out of practice" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case out of practice = rusty*.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 RUSTY* mean?
RUSTY* adjective- Marked or corroded by rust.
- Of the rust color, reddish or reddish-brown.
- Lacking recent experience, out of practice, especially with respect to a skill or activity.
- Of clothing, especially dark clothing: worn, shabby.
- Affected with the fungal plant disease called rust.
- Discolored and rancid; reasty.