Hi,
I’m trying to use a script that is entered in an text custom fields on every item, i try using a embed to display it, but it return the script as texte, any idea ?
Thanks 
You need to HTML decode that content so that the browser sees it as code that it should process. Unfortunately, that generally requires a bit of a hack.
Very important, if you’re doing this from a CMS collection, be aware that whatever is in that field will be considered valid script, and executed. If you’re e.g. taking form posts, and collecting them into your CMS like a blog commenting system might do, you’ve just set yourself up for a script injection attack. Make sure you control that script field personally.
I think this is the approach I used to handle podcast embeds.