Clue: Travelling west, go overseas regularly for machine requiring slave labour? (5)
Answer: SERVO
Explanation: Travelling west, go overseas regularly for machine requiring slave labour? (5)
Regular letters in "g**O **o**V**e**R**s**E**a**S**", "travelling west" (ie from right to left) 
I'm no mechanic, so don't know anything about servos, but the wordplay workd and a quick Google search does bring up terms such as "servo slave" and "slave cylinders".