Google rarely overlooks anything, and if click through rate is a ranking factor, I mean why shouldn't it be, I am absolutely sure that Google has a complex algorithm for this and is not only comparing position in result pages with clicks.
I am not a SEO expert or guru, but this is how I see things: if your site gets a lot of clicks for "orange", it means that the page is well optimized and people find the content of this page relevant and useful when searching for "orange". In this case your site's ranking will probably increase in serps for "orange". I don't see how it will or could be affected the ranking for "apple" too. Well, come to think about it, as I said before, I tend to believe that Google has an algorithm for this, and in some form it might be taken in consideration the rankings of all the pages have for different keywords.
I might be wrong though, so don't rely solely on my comment...
