Prefix meaning "self" (4)
I believe the answer is:
auto
'prefix meaning self' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for auto that I've seen before include "Car (mostly US)" , "Prefix to denote self or same" , "Prefix denoting by or of the same person or thing" , "Car (chiefly in US)" , "Motor vehicle, in short" .)