Tough policeman's Yard file note (4,4)
I believe the answer is:
hard copy
'file note' is the definition.
(note written on a file)
'tough policeman's yard' is the wordplay.
'tough' becomes 'hard' (associated in meaning).
'policeman' becomes 'cop' (cop is a kind of policeman).
'yard' becomes 'y'.
'hard'+'cop'+'y'='HARD COPY'
(Other definitions for hard copy that I've seen before include "e-mail, say, printed out" , "printed version" , "Computerised data that's been printed out" , "PC paper?" , "print" .)