Former inspector's report for the Treasury (9)
I believe the answer is:
exchequer
'the treasury' is the definition.
('exchequer' can be a synonym of 'treasury')
'former inspector's report' is the wordplay.
'former' becomes 'ex'.
'inspector' becomes 'checker' (checker is a kind of inspector).
'report' shows a homophone (sound like).
'checker' is a homophone of 'chequer'.
'ex'+'chequer'='EXCHEQUER'
'for' is the link.
(Other definitions for exchequer that I've seen before include "Bank of England account" , "Treasury accounting department" , "Government funds" , "finance department" , "where the money goes" .)