Aforementioned model leaves sober (4)
I believe the answer is:
said
'aforementioned' is the definition.
(I know that aforementioned can be written as said)
'model leaves sober' is the wordplay.
'model' becomes 't' (Ford Model T car).
'leaves' indicates named letters should be taken away.
'sober' becomes 'staid' (synonyms).
'staid' with 't' taken out is 'SAID'.
(Other definitions for said that I've seen before include "Averred" , "Announced; Egypt. Port" , "Spoke" , "Spoken" , "Stated" .)