Endless subject of discussion with others who oppose us? (4)
I believe the answer is:
them
'others who oppose us?' is the definition.
'them' can be an answer for 'others' (I've seen this in another clue). I'm not sure about the rest of the definition.
'endless subject of discussion' is the wordplay.
'endless' indicates the central letters.
'subject' becomes 'voter' (voter is a kind of subject).
'of discussion' becomes 'hem' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle of 'voter' is 't'.
't'+'hem'='THEM'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for them that I've seen before include "Certainly not us, the other lot" , "Those people (as object)" , "people objectively" , "... in another case, they" , "Let -- eat cake" .)