The most common and most likely answer to this crossword clue is the 3 plus 3 letter word BIG TOE
I've seen this crossword clue in The Times
B
I
G
T
O
E
More clues leading to the result BIG TOE
Buddy explains!
The straight part
We know that "The one that went to market on foot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the one that went to market on foot = big toe.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.