Car numberplate? One working part (6)
I believe the answer is:
region
'part' is the definition.
(I know that part can be written as region)
'car numberplate? one working' is the wordplay.
'car numberplate?' becomes 'reg' (I can't justify this - if you can you should believe this answer much more).
'one' becomes 'i' (Roman numeral).
'working' becomes 'on' (on can mean working or activated).
'reg'+'i'+'on'='REGION'
Can you help me to learn more?
(Other definitions for region that I've seen before include "Area, location" , "Wide area" , "Area of country" , "Ignore (anag) -- expanse of land" , "Area having definable character" .)