It may help to look at this issue as part of the reasoning behind Quine's holism thesis. Imagine Quine considering to give up the special status of even logical and mathematical truths, and make them susceptible to revision, if needed, in order to accommodate sense experience. The only obstacle could be if a source of truth other than experience could be clearly isolated.
But hey, analytic statements do exemplify, apparently, another source of truth. What source? Well, analytic statements have been said to be true in virtue of meanings. Well, is there something substantial behind these words, or are they mostly façon de parler? This is the "unclarity" that Quine is pursuing in Two Dogmas of Empiricism. And when Quine proves that notions like "meaning" and "synonym" are not more basic than "analytic", and therefore cannot explain it, the whole chain falls out like dry leaves. Analytic truth can be explained as an instance of truth about meanings, no more than truth about meanings can be explained as an instance of analytic truth. The truth of (so called) analytic statements remains firm, of course, but its source remains obscure. And so Quine can safely proceed with his bold empiricist holism thesis.