someone who protects a place against attack, or who believes in and supports a person, idea, plan, etc.

The city's defenders were outnumbered by the besieging army. 在数量上，守城者不及围城的军队。

So far they have found few defenders of their point of view on campus. 到目前为止，他们在学校里没找到几个支持他们观点的人。

someone in a sports team who tries to prevent the other team from scoring points, goals, etc.

The Brazilian attack put France's defenders under pressure. 巴西队的进攻给法国队的后卫施加了很大的压力。