To speak clearly or distinctly — to say something so that it is easy to hear or understand.
聞き返されないように、もっとはっきり言ってください。
Please speak more clearly so you don't have to be asked to repeat.
外国人に説明するときは、ゆっくりとはっきり言うと親切だ。
When explaining to foreigners, it's helpful to speak slowly and clearly.
指示をはっきり言っておかないと混乱するよ。
If you don't give clear instructions, it'll cause confusion.
To put it bluntly or frankly — to speak one's mind directly without beating around the bush.
はっきり言うと、その案には賛成できない。
To be frank, I can't agree with that proposal.
彼女は遠慮せずに問題点をはっきり言った。
She pointed out the problems bluntly without holding back.
はっきり言って、時間の無駄だと思う。
Frankly, I think it's a waste of time.