JJ - if you decide to add a IWB holster to your clipped G21 then I 100% wholeheartedly recommend a Cross Breed Super Tuck.
I carry a Sig Sauer P220 SAO in one all the time. Must comfortable IWB holster I've owned. Makes my full size 45 disappear under minimal clothes. Very secure as well.
Does the clip fit over the holster well or do I need to take it off when I use the holster?
