Clen can be a great fat burner but I only use it at key times with my athletes like in the prep phase.
You do not won't to over do its use or depend on it like a pre workout which is something many people do
you have to always consider long term heart health
the best protocol that I have found is the following
I like to run clen for 3 weeks on 1 week off
On the 3rd week I also have my athletes to take 1 tablet of Benadryl at bedtime
then the 4th week is off everything
then repeat