I have discussed this earlier with another student, that to remove ambiguity from such a sentence one has to rely on punctuation. "Parliamo chiaramente" would, in speech, mean three different statements depending on the tone of voice. In writing however, one is dependent on punctuation to remove ambiguity.
"Parliamo chiaramente." = We speak clearly.
"Parliamo chiaramente? = Do we speak clearly?
"Parliamo chiaramente! = Let's speak clearly!
I am not fond of this as a teaching tool, though, as it's overly simplistic and doesn't reflect how the language is really used. In actual practice, it is extremely common to have the command form of the verb used without an exclamation point (you see it every single day in written Italian), and there's no prescriptive rule against it either. It doesn't make sense to teach language learners a punctuation "rule" that doesn't reflect linguistic reality.
I would say that the three example sentences in my previous comment demonstrate the linguistic reality, and necessity for punctuation. For more reading please see the following link. https://dictionary.cambridge.org/grammar/british-grammar/punctuation
Now, in retrospect, I think "Let's speak frankly" should have been accepted.