Bus driver for Bart and Lisa (4)
I believe the answer is:
otto
'bus driver for bart and lisa' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for otto that I've seen before include "Four-stroke cycle -- palindromic name" , "Rose oil - Holy Roman Emperor" , "Reversible German" , "Oil made of rose petals" , "____ Preminger, US film director born in Austria" .)