So I guess you tried Crossfiring a discrete GPU to an IGP? Or what do you actually mean? I don't understand
If you are make sure you set the main graphics to 'PCI-E' and connect the cable from the monitor to the card instead of the motherboard. Then there should be a hybrid crossfire option there when you open CCC.
Note: this is just a 100% guess, it may not work. I never try these hybrid crossfiring