Following retreat Gospel writer in state (7)
I believe the answer is:
denmark
'state' is the definition.
(Denmark is an example)
'following retreat gospel writer' is the wordplay.
'following' says to put letters next to each other.
'retreat' becomes 'den'.
'gospel writer' becomes 'mark' (I've seen this before).
'den' next to 'mark' is 'DENMARK'.
'in' is the link.
(Other definitions for denmark that I've seen before include "North European country" , "Hamlet, Prince of . . . . . . . (7)" , "A country of dark men?" , "Mark end of the country" , "Aarhus is its second-largest city" .)