No nonsense shown over one old American film (9)
I believe the answer is:
notorious
'film' is the definition.
(1946 film)
'no nonsense shown over one old american' is the wordplay.
'nonsense' becomes 'rot' (I've seen this before).
'shown over' says the letters should be written backwards (letters flipped over).
'one' becomes 'I' (Roman numeral).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'american' becomes 'us' (abbreviation for United States).
'rot' written backwards gives 'tor'.
'no'+'tor'+'i'+'o'+'us'='NOTORIOUS'
(Other definitions for notorious that I've seen before include "worthy of shame?" , "Famous for misdeeds" , "having a terrible reputation?" , "Hitchcock film" , "of ill-repute" .)