Pre-programme car, 50% less consumed (8)
I believe the answer is:
automate
'pre-programme' is the definition.
(make something automatic)
'car 50% less consumed' is the wordplay.
I cannot really understand how this works, but
'car' could be 'auto' (automobile) and 'auto' is located in the answer.
'consumed' could be 'ate' (to eat is to consume food) and 'ate' is found within the answer.
A single letter 'm' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for automate that I've seen before include "Mechanise to make something work without human intervention" , "'Control something using machines, not people (8)'" , "Convert to robotic operation" , "Cause to function without direct human control" , "Make (a device) work with little human control" .)