Coldly efficient, but he makes two rock bottom starts (5)

I believe the answer is:

robot

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for robot that I've seen before include "Humanoid machine" , "Automatic worker?" , "programmed servant" , "Unpaid worker" , "Mechanical man" .)

Want a hint initially instead of a full solution? Install my app