Winny and clen for endurance? Not everyone has joint problems with winny, but a lot of people do. Not really something you'd want as a tri-athlete but that's your choice. The worst advice was clen. Clen is a horrible idea for someone who is keeping their heart rate up for that long
I'd opt for a sarms stack. You can greatly increase your endurance and fat loss with GW-50156 and build a few pounds of lean muscle with S4 and Ostarine. This is a perfect stack for endurance athletes. Check out Sarms1
Yea whoever told you to take winny and clen should be beaten. Winny will most likely be hard on your joints and clen is just a terrible compound to begin with. If you want an endurance chemical look into Albuterol instead - same style of effects but no enlarging of the cardiac muscles.
Like these guys said too, Sarms1 GW-50 is really all you'll need. Very potent and amazing for endurance. Literally built for endurance and anti-catabolism