English also has its share of words that can mean different things. Like "mean", for example. It can be the definition or intention of a word/phrase/sentence, or it can be "cruel" or it can be "average". "Run" can be "to move quickly" or "a tear in fabric" or "to compete, as in politics" or "to operate, as a car or computer program".
I believe the placement of the word "propre" in a particular sentence will signify its context and meaning.
If propre comes before a noun ("ma propre femme"), it means "own."
If propre comes after a noun/verb combination ("nous sommes propres"), the word signifies "clean."
I hope this helps my beginning peers in learning.