The team is looking to 'defend' its national title. [=to win the national title again]
As a U.S. senator, it is my responsibility to 'defend' [='uphold'] the Constitution.
She successfully 'defended' her championship. [=she won the championship again]
(..) What is this? Love Your Underprivileged Brother Week? I want you to tell me why you changed your vote. Give me reasons. I don't have to defend my decision to you. There is a reasonable doubt in my mind. Reasonable doubt? Nothing but words. Look at this. The kid you just decided isn't guilty (..)1957 12 Angry Men