Brayford has been linked with West Bromwich Albion.
Responding to the speculation, Clough said: "Are they? Is that all, £3million? We are looking to build with young players throughout the squad and John is part of that.
"When you get players like John who come into the Championship for the first time, people watch them for a season and wonder 'can they do it again, was it a fluke?'. I think the way John has started in the first six games this season suggests he can do it again."