Promotional industry replacing content of billboards in part of South Dakota (8)
I believe the answer is:
badlands
'part of south dakota' is the definition.
(I know that Badlands is part of South Dakota)
'promotional industry replacing content of billboards' is the wordplay.
I cannot really understand how this works, but
'content' could be 'ds' (DS is an example) and 'ds' is located in the answer.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Another definition for badlands that I've seen is " Barren region of South Dakota and Nebraska".)