Broadcast that is going after voting system — that's plain (7)
I believe the answer is:
prairie
'plain' is the definition.
(type of plain)
'broadcast that is going after voting system' is the wordplay.
'broadcast' becomes 'air' (synonyms).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'going after' says to put letters next to each other.
'voting system' becomes 'PR' (proportional representation).
'air'+'ie'='airie'
'airie' after 'pr' is 'PRAIRIE'.
'that's' is the link.
(Other definitions for prairie that I've seen before include "Continental grassland of N America" , "Open grassland in the USA" , "Grasslands" , "Great grassland area" , "Large treeless tract of grassland" .)