Clue: Get instruction to sheepdog (4,2)
Answer: COME BY
Explanation: Definition: Get
 Not sure about this: "come-bye"(an instruction for a sheepdog to go clockwise round the sheep) has no alternative spelling that I can find. Is "get" doing double duty as definition and homophone indicator?
Defn: …/to acquire, as in "how did you come by that thing".