Policeman attached to Yard providing material for newspaper? (4)
I believe the answer is:
copy
'material for newspaper?' is the definition.
'policeman attached to yard' is the wordplay.
'policeman' becomes 'cop' (slang term).
'attached to' is a charade indicator (letters next to each other).
'yard' becomes 'y' (abbreviation).
'cop'+'y'='COPY'
'providing' is the link.
(Other definitions for copy that I've seen before include "Imitation or reproduction" , "Imitation or matter for printing" , "Transcript" , "Replica; text for printing" , "stuff to be published" .)