how do i know whether a course is in clearing?

I know you can search on UCAS which I’ve done but I heard not all the courses listed as in clearing in UCAS actually have spaces available, I can’t go through clearing until results day as I have conditional offers from my firm and insurance. I don’t want to waste time calling unis that don’t actually have places but don’t know how to find out if they’re in clearing or not (sorry if this is a stupid question)