Can T3 and/or clen be usefull during a bulk cycle?
I would spend my money elsewhere, since the purpose of bulking is to eat more calories than you are metabolising. Not metabolise more than you are eating (which would be a cutting cycle).
Small doses MAY work but like banana eater said spend your mone elsewhere.
I have heard about 12.5 mcg of T3 will boost muscle building and fat burning. You would simply have to upregulate your calories accordingly. Clen however is anabolic for some and not for others. I would definately hold off on the clen. It is hard enough for most people to eat enough calories while bulking with out adding t3 and clen.