Exile making one a politician, for instance (7)

I believe the answer is:
example
'instance' is the definition.
(synonyms)
'exile making one a politician' is the wordplay.
I cannot really understand how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is present in the answer.
'politician' could be 'mp' (Member of Parliament) and 'mp' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for example that I've seen before include "Illustrative case" , "Something to be imitated" , "Ideal - specimen" , "Illustration or paradigm" , "Specimen, sample" .)
