The 26-year-old former Crystal Palace youngster joined Stags this summer after three seasons for League One MK Dons and Clough said: “He is someone we have admired for a while.
“He has been around and played a good standard and he is a good footballer. He is also a very articulate, intelligent lad and someone we feel is going to fit in.
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“We beat off quite a bit of competition and we are very, very excited about Hiram joining us.”
Clough continued: “He can play anywhere in the midfield. He can play the more of a defensive role or anywhere across that midfield three or even a little bit further up at times.
“He is just a good footballer who can adapt.
“As to why he chose to come to us, people are aware of how well we've done in the last seven months – not just the results but how we've played. That's how you get to attract people like Hiram.”
Clough confirmed Longstaff would not be returning after the end of his loan spell.
“I think that one was a freakish one and a fluke to get someone like Matty,” he said.
“I would expect him, if he doesn't stay in the Newcastle squad, to play Championship or the very top of League One.”
Clough has just returned from holiday but said it was business as usual at times still.
“It was nice to get away. I think everyone needed to have a little break but, as always, your phone is still on and there is business to do,” he said.
He is now working on getting four players – two on loan from a Premier League club – in as quickly as possible with the squad returning for pre-season tomorrow.