Applying for clearing if I have a conditional?

Sorry if this is a stupid question but id rather be sure!

I currently have a conditional offer for uni, which ill need to do an assessment for on August 25th, so wont expect to get my results for a week or two afterwards.

I keep getting emails from UCAS asking me to sign up for this new clearing scheme, and its given me the impression it might be too late to sign up for at the start of September.

Im just wondering can I sign up for this even though I still have a conditional, or is it better to see how my exam goes and try clearing the usual way?

Hopefully I wont need to use any of this anyway but id rather be safe!