I started t3 at 20mcg a day...then every 5 days upped it 20 more mcg until I hit 100mcg a day...then tapered back down.
The clen I started at 40mcg 2days on 2days off, then I increased it each week until I hit 100mcg, then tapered back down each week
I did cardio 4 times a week and trained only 2 times a week.
I wasn't worried about muscle, just losing fat.
I didn't notice any muscle loss...that's not saying I didn't have any...just that if I did, it was very little (and I flex everytime I go into my bathroom

). I definitely didn't have any muscle gain during that period.
After that cycle, I took 2 weeks off (went on vacation) and when I came back, I was stronger than I'd previously been...not sure how that happend, maybe my body just needed a break.
Anyway, next time I use t3 and clen, I'm definitely gonna use something else (eq, winny, something...not sure yet), but if you're just doing clen and you want to add in the t3, I think it will be fine.