Barrier formed by politicians? (5,4)

I believe the answer is:

party wall

I'm a little stuck... Click here to teach me more about this clue!

'barrier' is the definition.
(I know that party wall is a type of fence)

I don't understand the remainder of the clue.

(Other definitions for party wall that I've seen before include "That shared by two houses" , "Divider of joined buildings" , "Divider common to two rooms or buildings" , "may be shared between neighbours" , "Boundary" .)

I've seen this clue in The Mirror.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.