You want just one card?

Normally one would do multiple up for this sort of thing...but

define the page size as the size you want the card to be..3-5/8 x 2-1/4 or
whatever. Then print with crop marks on a letter page.

NOW..if when you set up the document you told it you wanted 10x or
something..there's the problem. Set it as page setup > Publication type
custom (usse the final trim size of the card) and when you go to print print
it on letter with crop marks.

i think this should work.