"They're a key stakeholder to Cliffs..."

Meaning...shareholders???

No, there's a difference. Shareholders have a direct financial stake in the company due to effective ownership of a part of the company, by virtue of the shares that they own.

Stakeholders include any person or entity that has vested interest in a company. Actually, "vested" might not be a correct use of the term. Basically though, stakeholders would include shareholders but would also include other people to make it a bigger group, ie. everyone who is directly affected by the operations of the company. So stakeholders can include people who live on property near the operations, suppliers, customers, government, financiers, employees, etc. Basically, anyone who is affected when the corporation makes decisions.