The term "defence secretary" refers to a high-ranking government official who is responsible for overseeing and managing the military and defense affairs of a country. Full definition
He said he'd heard she was offered the job of shadow defence secretary and turned it down - which could explain the long delays. (mirror.co.uk)
She looked at the former defence secretary as though he were a piece of dirt. (politics.co.uk)
As defence secretary in 2013 he attracted criticism by talking about «a real sense of anger among many people who are married» who felt the gay marriage law would change the institution. (theguardian.com)