Clarke returned to bat on Wednesday having retired hurt shortly before tea on day one of the first Test at Adelaide.
Though clearly inhibited by his persistent back problem, Clarke made 128 in an emotional first innings back since the death of international team-mate Phillip Hughes.
Smith himself reached 162 not out to leave the hosts on 517-7 at the close of day two, but it was Clarke's knock that he was keen to reflect on
"He just came out and played beautifully," said Smith.
"I think a few shots hurt him, but he got himself into as many good positions as he could and he manipulated the field a little bit as well.
"He has done amazingly over the last couple of weeks, spending the whole time by Hughesy's family's side.
"Just the strength and courage he has shown through those times was unbelievable.
"He must be mentally drained coming into this game, but the way he played speaks the world of that guy. He came out here and tried to do something for Hughesy and he certainly did that."