Chosen exam about system of appointing MPs? (9)

I believe the answer is:
electoral
'system of appointing mps?' is the definition.
I can't tell whether this definition defines the answer.
'chosen exam' is the wordplay.
'chosen' becomes 'elect' ('elect' as an adjective can mean chosen).
'exam' becomes 'oral' (spoken academic test).
'elect'+'oral'='ELECTORAL'
'about' acts as a link.
Can you help me to learn more?
(Other definitions for electoral that I've seen before include "of constituents" , "Relating to the voting system" , "one kind of college" , "List of voters" , "concerning voters" .)
