I think it's because "make clear" forms a semantic unit equivalent to "clarify". "buy new" exhibits no such coherence. Other than that, I don't know.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
I am puzzled at the difference in ...
Hmmm. So am I.
And yet ...
We sweep a floor until it becomes clean.
We don't buy a book until it becomes new.
Is there anything worth pondering in this observation?
CJ