By definition Cross-genre writing is hard to define. Every person I know who writes this type of story has their own version of what makes a cross-genre story cross-genre.
I take the high road.
Technically, my stories are cross-genre which is the blending of two distinct genres. Such as what I write; Contemporary Action Fantasy Romance. Action Fantasy is its own genre. Romance is its own genre. I meld the two together in a 50/50 wordcount split to create a story that moves, has all the wonders of Fantasy, but also has a Romance happening at the same time.
In cross-genre story telling, there are also two plots.
It is inevitable that one of the genres ends first and the other last. In my case the Romance ends last. This deems my stories as Romance, but many Fantasy readers will enjoy it too.