Animal keeper, all but big, is gone (6)

I believe the answer is:

mahout

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 mahout that I've seen before include "Indian elephant driver" , "Elephant-driver" , "jumbo? I'll see to it" , "Keeper and driver of elephants" , "Person navigating Jumbo" .)

I've seen this clue in The Hindu.

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