The most common and most likely answer to this crossword clue is the 7 letter word STANDEE
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More clues leading to the result STANDEE
Buddy explains!

The straight part
We know that "One on their feet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one on their feet = standee.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 STANDEE mean?
STANDEE noun- Somebody who is forced to stand up, for example, on a crowded bus.
- A free-standing, rigid print (usually life-sized), for instance of a celebrity, often displayed for advertising and promotional purposes; a cut-out.