The Magpies, who have already added Sven Botman to the ranks at St James’ Park this summer, are trying to offload a number of out-of-favour players.
They are ready to let Clark leave and have agreed to loan him to Sheffield United for the upcoming campaign.
The deal is progressing quickly and Clark is due to undergo a medical with Sheffield United within the next 24 hours ahead of sealing the switch.
Clark is out of contract at Newcastle next summer and the move effectively ends his spell at St James’ Park.
Newcastle signed the 32-year-old from Aston Villa in 2016 and he has made over 100 league appearances for the Magpies.
He clocked 13 outings in the Premier League for Newcastle over the course of last season, being booked twice.
Clark has played in the Championship before and won the division with Newcastle in the 2016/17 campaign.