The 19-year-old stopper was plucked from schoolboy football just over two years ago and went on to earn a two-year professional contract with the Magpies.
"We talk about Fraser at the club and we believe he is the most improved player over the past 18 months," Clark told Newcastle World TV after his team's defeat to Middlesbrough.
"That's all credit to the coaching staff at the club and also to Steve Harper and Shay Given who look after our young keepers.
"Some of the saves Fraser pulled off against Boro were of the highest quality.
"If he improves at the rate he has so far then we could have another fantastic keeper to add to what we have got already."