If I say ''what kanji is feather'' would a Japanese instantly know the Kanji?

Question:

Or would they need to think for a moment? I'm trying to get in the head of a native kanji expert.

Answer:

Well it just depends on the word sometimes and meaning. Simple ones can be done easily. Others you might need to be more specific, and others might require thinking to remember.

If you said "East" 東 yeah most people will know that instantly.

If you said "big", well it depends on what kind of big you want. You can get the standard kanji for big, but did you mean "fat", or did you mean "thick"? It can get specific so you need to be specific.

Basic "everyday" kanji shouldn't be a major problem, but you said "anyword", well things can get more complicated even for English folks. Ask an English person to spell dermatofibrosarcoma_protuberans (a medical condition), then you're going to have some problems, same for Japanese.