The half-timbered gatehouse, below, was built around 1640.
Unfortunately, there's little left of this formerly magnificent Marcher castle. There are more pictures and information here - when I was there, much of the ruins were covered in scaffolding, and while I was delighted to see that efforts are being made to stop them deteriorating further, it did tend to ruin the photo opportunities somewhat.
Roger Mortimer attacked and captured Clun in May 1321, during the Despenser War (the Earl of Arundel, Edmund Fitzalan, was an ally of Edward II and Despenser). In January 1322, the castle was taken from Mortimer by a Welsh force led by his enemy, Sir Gruffydd Llwyd.This board shows Clun as the Fitzalans would have known it: