Despite being just 17 years of age, the England U19 international is taking in his third season as part of the senior set-up at Pride Park.
He does, however, face stiff competition for places from more experienced performers in creative roles.
Taking that into account, Derby hope the opportunity to get regular game at League Two table-toppers Chesterfield will see Bennett returned to them in a stronger position to push on towards a bright future.
McClaren said in the Derby Telegraph: "Mason needs experience, he needs more game. It is a great move for him.
"He needs to go above U21 level matches now and test himself in League football.
"We see him as a big player for us next season. We want him to get some experience."
Bennett said of his switch: "I pounced on the opportunity when my agent asked me if I wanted to join Chesterfield. I said 'yes' straight away.
"I'm buzzing because I want to get in front of a crowd again and show what I can do.
"I've been in and out of the team this season and I need to start playing regularly."