Sure you can add caraway seed to secondary. Caraway seed & apple go together like bread & butter! A lot of German food recipes use both caraway & apple.
https://www.google.com/webhp?source...UTF-8#q=German recipes with caraway and apple
I like to add a tablespoonful of caraway seed to a 6 gallon batch of graff. I usually leave it in for about a month, but the longer you leave it in, the stronger the caraway profile. You'll need to taste it periodically to see when it reaches the flavour profile you like. I've even experimented with adding a couple seeds to the bottle at bottling time. Those bottles had a very strong caraway flavour, almost like aquavit.
I've added it to primary too, both work well, though you'll get a better caraway flavour in secondary with cider. You can add less & leave it in longer, or you can add more & get that flavour a bit faster. Try a taste test by putting a good sized pinch of caraway seed in a glass of apple juice & pop it in the microwave for a minute or 2. Let it cool to room temp before you taste it. It won't taste exactly like it will in a cider, but it'll give you a rough idea as to how the flavour of caraway works with the flavour of apple. I like it quite a bit, if you like caraway, I'll bet you'll like it too.
Regards, GF.