Views accordion grouping on taxonomy
From your question, I'm assuming that you've already created view and set everything.

You just need to do some Format settings for Views Accordion in your View.

Here are the steps to make your grouping field as the "header" or "trigger" of the accordion action.


Go to  Format: Views Accordion Settings and select Grouping field.
Check "Use the group header as the Accordion header"


I've tested it myself. It works as you expected.