Concentration is not being consumed when clearcasting Arcane explosion.
Concentrated Power: Clearcasting makes your next Arcane Missiles channel 20% faster or Arcane Explosion echo for 40% damage.
Concentration: Arcane Blast has a chance to grant Concentration, which causes your next Clearcasting to not be consumed.
When you proc concentration, it will lock you out of being able to use clearcasting procs when trying to use arcane explosion, which means you are locked out of echoing your arcane explosion so long as you have concentration.
I feel like this is an oversight because the wording of the talents imply it should function.