Protest march about renegade politician? (8)

I believe the answer is:

democrat

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'politician?' is the definition.
(Democrat is an example)

'protest march about renegade' is the wordplay.
'protest march' becomes 'demo' (I can't explain this - if you can you should believe this answer much more).
'about' becomes 'c' (abbreviation for 'circa').
'renegade' becomes 'rat' (I've seen this before).
'demo'+'c'+'rat'='DEMOCRAT'

Can you help me to learn more?

(Other definitions for democrat that I've seen before include "Member of US political party" , "Cleveland?" , "Political type" , "American politician" , "Person who believes in government by and for the people" .)

I've seen this clue in The Independent.

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