A "watchman" watches outside his city to see if danger is coming. The prophet warning the people when they are sinning and are in danger of having his God punish them is spoken of as if he were a watchman for the city. Alternate translation: "The prophet is like a watchman for God over Ephraim" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This refers to prophets in general that God has appointed. Alternate translation: "Prophets are" or "True prophets are" (See: [[rc://en/ta/man/translate/figs-genericnoun]])
A "bird snare" is a trap used to catch a bird. This means the people of Israel do whatever they can to stop God's prophet. Alternate translation: "the people set a trap for him wherever he goes" or "the people do all they can to harm him" (See: [[rc://en/ta/man/translate/figs-metaphor]])