Even though it's completely fine and great and clear if you release the T here.

如果你在这里发 T 音就清楚的发音。

His pronunciation is clear, but he has a heavy accent which makes him difficult to understand sometimes.

的发音清楚，但有重的口音，这有时理解困难。

For pronunciation, it's mostly clear, but not always clear; he would probably get 5.

发音大都是清楚的，但不是总是清楚，那么可能得5分。

And you want to be in a place of power where you know that you pronounce things clearly depending on who you are speaking with.

如果你想做一个有力的演讲，你知道你的发音清楚取决于你和谁说话。