Last year's account of police? (3,4)
I believe the answer is:
old bill
'police?' is the definition.
(I've seen this before)
'last year's account' is the wordplay.
'last year' becomes 'old' (I can't explain this - if you can you should believe this answer much more).
'account' becomes 'bill' (billing is a kind of accounting).
'old'+'bill'='OLD BILL'
'of' is the link.
Can you help me to learn more?
(Other definitions for old bill that I've seen before include "British Bobby" , "forgotten account" , "pound note?" , "Policeman" , "Police (slang)" .)