Country's pro-Labour slogan? (5)
I believe the answer is:
congo
'country's' is the definition.
(Congo is an example)
I don't understand the remainder of the clue.
(Other definitions for congo that I've seen before include "Wide river" , "former African nation" , "Brazzaville its capital" , "African river flowing into the South Atlantic" , "It was known as Zaire" .)