I'm gonna' get slammed, but here goes.... Clen does promote weight loss, but you really gotta' follow the protocol.
1) Why .... why would you run a life threatening drug if you don't need to, and I accept that you just need to, many people don't.
2) Goals... what do you think Clen is going to give to you?
3) Damage... what damage do you think Clen will do to your body?

In my experience, Clenbuterol with another substance will take a body to weight loss, but at a cost. Explain to me the physiological costs, and I will ask members to help you unlock the keys. 15% BF,, you are just on the borderline. You are pretty close to understanding.

Before helping you, I would love to see your reply to @Axzel69 reply, even I an looking, but you really need to consider your long life... it will mean something, sometime.

Why not run an ECA/ECY stack instead it's better and doesn't have the risk profile clen has with shit like myocyte necrosis....
My suggestion is skip clen and do DO fasted cardio upon waking with an ECY (sub the Yohimbine for Alpha-Yohimbine for less sides) and then ECA another 2-3 times during the day. Watch the Dosage of Yohimbine with the Ephedrine since it will dramatically increase its effectiveness (start with a smaller dose if you haven't run this before, like 50% dose of each)

So something like this:

First dose:
Ephedrine: 12.5mg
Caffeine: ~200mg
Alpha-Yohimbine (rauwolscine):~1mg-2mg
Asprin: 81mg (one baby asprin)

Second dose:
Ephedrine: 12.5mg
Caffeine: ~200mg

Third dose:
Ephedrine: 12.5mg
Caffeine: ~200mg

See how you tolerate that and then increase the Ephedrine to 25mg. If you dont know how you tolerate stimulants err on the side of caution, If you haven't taken ECA before start without the Yohimbine and see how you respond You may not even need the Yohimbine at all ECA is very strong.

As with all stimulants it will increase heart-rate just start slow and get a feel for it, watch your heart-rate and especially during cardio.

So the other thing you will get with ECA that you wont get from Clen is the hunger blunting effect, it makes cutting a little easier some like the energy from it better than Clen as well.

Now if you are dead-set on Clen so be it (many people use it I wouldn't touch the stuff) You want to start slow and see how you react like 10-20mcg and see how you respond, work your way up if you respond well increasing by 10-20mcg each day up to like 100mcg or till you feel its too much then taper back down (less is more with any of this stuff, use the lowest dose that will achieve your goals).

Again though I suggest skipping the clen and giving ECA/ECY a try.