Knight doctor for keeping calm given final twist? (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

MD (doctor) around (for keeping) ORDER (calm) with last two letters switched (given final twist) I didn’t quite clock the wordplay here, but I remembered MORDRED as being a name from Arthurian legend, and assumed he (?) was a ‘knight doctor’. Turns out MORDRED was knighted.