If you're writing A Series of Unfortunate Events, it works. Because the purpose is to educate the reader (or allow the reader to be the one that says "I know what X means"). If you're writing a serious book, it's annoying.
In real life, if someone is speaking with someone who doesn't know the vocabulary, they restate things in a way that doesn't draw attention to the person's deficit.
Character 1: ...network of clandestine tunnels under the city...
Character 2: looks confused
Character 1 (or 3): After we find these
hidden tunnels, we can...
But wow is that tedious. Just leave it out. Even if it's done more seamlessly, without showing the confusion. In that example, the word can be figured out by context. In other cases, not so much.
For instance, just last night I was at a presentation by high school students about AP class offerings at the school. After the second one mentioned "a-push" I called out "what does 'a-push' mean?" But I wouldn't have if it wasn't such a small audience or if they'd been on a stage instead of just one side of the library. Context matters for the confused listener too. (BTW, it means AP-US, the Advanced Placement class for American History.) But I bet you're all bored simply reading my example...you wouldn't want to see it in a book. Especially not over and over.
If you continue to have people explain things to the uneducated person, after you've established their situation, you risk the reader feeling that you're doing it either to provide unnecessary exposition or to poke fun at the bubble-headed woman who doesn't understand what the men are talking about (this is true even if some of the characters explaining things are women). It's a stereotype and one that has been used in a lot of books. Where the dumb woman is there just so the men can explain things.
Even if you take away all the gender issues with this stereotype, it's still an over-used technique. Dumb men aren't any more interesting than dumb women. Even if they're really smart but just don't have the required knowledge yet.
It would be one thing if you were using it to explain stuff the reader wouldn't know ("this is how to shut down the engine if the alarm sounds and how to troubleshoot things before you turn it back on" or "not there; make your cut just above the second set of triple leaves"), though it can get old there too.
You can have the character ask for clarification of more complex things that depend on vocabulary. Not "what does clandestine mean?" but more like "MITRE radar?" But use this sparingly. Twice is enough.
You can use other methods to show the character's lack of education. For example, she would speak with a lower level vocabulary than educated people. No native speaker makes a grammatical mistake in their language (unless they're misapplying something they learned in school) but what is correct in speech is often wrong in written language or in spoken language used by people with education. So she would speak correctly but differently. As she learns new words, she will start to use them, and sometimes might get them a bit wrong. Same for understanding what others say. Make these things subtle and be careful that they don't get distracting.