The defender missed out on a place in Eddie Howe’s 25-man Premier League squad for the second half of last season following the January arrival of Dan Burn from Brighton and Hove Albion.
And the 32-year-old, a mainstay of the squad during Rafa Benitez’s time as manager, is set to join Championship club Sheffield United on loan after being told to train away from the first-team group.
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Clark, signed from Aston Villa in the summer of 2016 following the club’s relegation to the Championship, has made 129 appearances – and scored 11 goals – for United.
Howe spoke about Clark’s situation last season after cutting him from his squad. United’s head coach said: "We’ve got Ciaran Clark, who is training with the group. His attitude has been first class. I’ve got no problem with him at all. Unfortunately, due to numbers, he missed out.”