It is unlikely that anything is broken or defective (but possible.)
What is more likely is that some bearing is slightly out of adjustment and moving under load. These are a PITA to track down. Often it is best to just re-adjust everything in the drive chain and see if the problem goes away. Also tighten chain ring and crank arm bolts and (yes) seat and seat post bolts. All of these can make noises while pedaling.

Oh, could also be a tight link on the chain.