If you are in the US, clenbuterol has been banned, so is therefore, an illegal drug. I don't know if it would show up on a drug test, but I certainly wouldn't take a chance.
Can clenbuterol show up on a drug screen test??
I am not real familiar with clenbuterol -- I do know it's used primarily for respiratory problems in horses and is not recommended for humans. It's totally banned in the US, although it appears that there ARE countries who allow limited use for humans.
Cytomel is a thyroid med and should never be used for weight loss purposes, since it can cause hyperthyroidism, which can be very dangerous. When used for thyroid issues, the patient should be continually monitored by a health care professional.