Use the clen during the steroid cycle. Adding clen into your PCT isn't a good idea. Clenbuterol is a very strong stimulant and can lead to muscle loss. It simple raises metabolism. It does not differentiate between muscle or fat. Especially during a PCT protocol when your hormone are low, it'll greatly increase your risk of loosing muscle.
What I would do is use clenbuterol with your cycle and then during your PCT, use stimulant free fat burners that won't have any of the muscle loss risk clen does. I personally like the stack of cardarine + n2slin.
https://www.needtobuildmuscle.com/store/Need2Slin-p50.html
Cardarine (GW-501516) - the best GW-50 - Evolutionary.org
Cardarine is drug that binds to the PPAR receptor and is non-hormonal. Cardarine increases the expression of genes involved in the expenditure of energy, stimulates glucose uptake in skeletal muscle tissue and burns fat by stimulating fatty acid oxidation.
N2slin is a non-stimulant fat burner and powerful nutrient partitioner. It increases insulin sensitivity of muscle cells and helps partition the food you eat into muscle cells and away from fat cells.
Take 20mg of cardarine gw per day. 10mg AM 10mg PM
Take 2 tablets N2slin 30 minutes before each meal you eat that contains a significant amount of carbohydrates.
Both are stimulant free and non-hormonal. You need to be careful with all these stimulant based fat burners. Overdoing it on the stimulants will greatly increase cortisol levels and lead to adrenal fatigue. Counterproductive to any fat loss or muscle building goals.