"C'est clair !"
Translation:That is clear!
Clair means light when it comes to colours: bleu clair = light blue.
C'est clair means it is clear as in no dout or no pollution.
Clair also means bright when it comes to light: un chambre clair
Or temps clair as in no clouds
Clair simply has many meanings and nuances. The word covers a whole column in my french-french dictionary.
But here, it doesn't really mean "pure", or "fair" or "bright", it's in the metaphoric sense. C'est clair = it's obvious/There's no doubts (as the "no clouds" you said) There's an expression in French. "C'est clair comme de l'eau de roche." =It's crystal-clear, litterally, it's as clear water from the rock/as spring water, maybe that expression is from this one.
It's gender bias in languages. In Spanish we say "está claro" on its own to convey that something is clear, an idea, a situation, etc. But if you say "está clara" on its own you are most likely referring to the lightness or brightness of something. I guess it is the same in French.
I put down, "I understand" and got it wrong. I was thinking of someone giving you instructions about how to do something, then saying, "C'est clair?" As in, is it clear? And me responding, "Oui, c'est clair." Or , yes, it is clear. Or yes, I am following you, or yes, "I understand"
Ah, I understand. The French (and all Romanic) language always defaults to Masculine when the gender is either unknown or mixed. So we can say She is clear=Elle est clairE and He is clear=Il est clair. But this sentence is unspecified so we must default to masculine because we don't and can't know grammatically what gender Ce\this/that/it actually is This is why Duo marked ClairE wrong, which is incorrect here. Does this help?
I believe the point is that "c'est claire" would technically be grammatically incorrect because "c'est clair" is an impersonal/general expression in which the gender is unspecified. And according to French grammar, when tbe gender is unspecified, you default ro masculine.
The context in this case is supposedly your knowledge of the language ;)