RnrActinTech saidwhat is your ultimate goal? Are you trying to get big or do you have another goal in lifting? I think this would help people answer your question.
If he's spinning for a hour, and is tiny, it doesn't sound like he's wanting to get big. (Yes, I read his profile.)
For the record, excess cardio, and calorie deficit, will burn the muscle off. HIIT is much more effective for developing cardiac threshold, leanness, and holding onto hard-won muscle.
Spin class is a prescription for skinny in most instances.
I just said what I said, because I don't think he's going to stop the spin class, and some weight lifting is better than none.