Spread in papers supporting City (4)
I believe the answer is:
laid
'spread' is the definition.
(I've seen this before)
'papers supporting city' is the wordplay.
'papers' becomes 'id' (identification papers).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'city' becomes 'la' (Los Angeles).
'id' after 'la' is 'LAID'.
'in' is the link.
(Other definitions for laid that I've seen before include "(Of dining table) set" , "Flattened by wind and rain" , "settled" , "Produced (an egg)" , "The clutch must be" .)