If that's a suggested accepted answer, you should use the report function instead of writing here.
For what it's worth, from the translations I see of -erevu, it seems to have slight negative connotations more in the realm of "clever, crafty, sly, cunning, deceitful" rather than more positive ones such as "intelligent, smart, bright, brainy", which I would suggest is closer to -enye akili.
That's just going from translations I see - I'm not an active user of Swahili, so take that with a grain of salt.
I think of it as "crafty, sly, cunning, deceitful", too. But both meanings are valid, according to the Dar es Salaam university dictionary:
1 intelligent, bright, brainy, genius, brilliant.
2 clever, cunning, crafty; shady, slick.
Why is just "clever child" not accepted. For exmple, one might say to a kid who quickly solves a puzzle, "Clever child!"
Normally, in English we would use an article, either "a" or "the". But if a child did something clever, we might exclaim "clever child!" without an article. It would be an exclamation, not a full sentence, which would require an article. But "mtoto mwerevu" is not a full sentence either.