IPA: /ˈfræŋkli/
KK: /ˈfræŋkli/
In a way that is honest and direct, without hiding feelings or opinions.
Frankly, I don't think that plan will work.
Frankly → It is formed from "frank" (from Old French *franc*, meaning free or open) and "-ly" (meaning in a manner of). The word "frankly" means in a manner that is open and honest, without concealment.
Think of being 'open' ('frank') when you speak, and the '-ly' just means the way you do it. So, when you say something frankly, you are being open and honest.