The most common and most likely answer to this crossword clue is the 9 letter word ASTRADDLE
I've seen this crossword clue in Financial Times
A
S
T
R
A
D
D
L
E
More clues leading to the result ASTRADDLE
- Across a street, right turn
- Turn red, sat awkwardly on top with a leg on each side
- Departs pub game that’s over, tucked into beer, ready for the off?
- Dotty sat on wobbly ladder with leg on either side
- Get right into a seat — with legs thus?
- Upon a seat gripping Trigger’s flanks?
- Keeping members apart, answer’s to adopt a non-committal attitude
- A seat keeping ends of their legs apart
- Alert dads moved, with legs wide apart
- A shot without substance, right before stump and across
Buddy explains!

The straight part
We know that "with leg on either side" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with leg on either side = astraddle.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 ASTRADDLE mean?
ASTRADDLE adverb- In a straddling position; astride.
- In a straddling position on.