Answer based on context:

A questionable role in the rebellion was played by Leonard Dacre, an early sympathiser of Mary. At the outbreak of the rebellion, he travelled to Elizabeth's court at Windsor to claim the heritage of his young nephew, the 5th Baron Dacre. After the latter's untimely death in 1569, this had descended to his sisters, all married to sons of the Duke of Norfolk. Dacre returned to Northern England, ostensibly a faithful partisan of Elizabeth, but his intentions remain unclear. After the retreat of the rebels, he seized Greystoke Castle and fortified his own Naworth Castle, where he gathered 3,000 Cumbrian troops and tried to keep up the appearance of good relations with the Queen. He held out against a siege of the royal army under Baron Hunsdon but then attacked the retreating army at Gelt River. Though Hunsdon was outnumbered, he charged Dacre's foot with his cavalry, killing 300-400 and capturing 200-300 men. Dacre escaped via Scotland to Flanders, where he died in exile.

Who subjected Dacre to a siege?
the royal army