The most common and most likely answer to this crossword clue is the 5 letter word GAMMY
I've seen this crossword clue in Independent
G
A
M
M
Y
Buddy explains!
The straight part
We know that "how’s your bad leg" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case how’s your bad leg = gammy.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 GAMMY mean?
GAMMY adjective- Injured, or not functioning properly (with respect to legs).
- Grandmother.
- A blowjob; fellatio.