Displaying this makes a van nationalistic, it's plain (7)
I believe the answer is:
savanna
'plain' is the definition.
(a savanna is a grassy plain)
'displaying this makes a van nationalistic' is the wordplay.
'displaying' indicates a hidden word.
'SAVANNA' is hidden in the letters of 'this makes a van nationalistic'.
'it's' acts as a link.
(Other definitions for savanna that I've seen before include "Large grassy plain with few trees" , "Tropical African grasslands" , "African grassland" , "Grassy (African) plain" , "Open grasslands of Africa" .)