Speech goes on about proportional representation (7)
I believe the answer is:
oration
'speech' is the definition.
(I know that oration is a type of oratory)
'on about proportional representation' is the wordplay.
'about' is an insertion indicator.
'proportional representation' becomes 'ratio' (I can't justify this - if you can you should believe this answer much more).
'on' placed around 'ratio' is 'ORATION'.
'goes' acts as a link.
Can you help me to learn more?
(Other definitions for oration that I've seen before include "A public or ceremonial speech" , "Making a speech" , "An eloquent speech" , "A formal or public speech" , "Address" .)