Former partner with large case (7)
I believe the answer is:
example
'case' is the definition.
(I've seen this in another clue)
'former partner with large' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'with' is a charade indicator (letters next to each other).
'large' becomes 'ample' (similar in meaning).
'ex'+'ample'='EXAMPLE'
(Other definitions for example that I've seen before include "Illustrative case" , "Thing characteristic of its kind" , "Prototype" , "Something illustrating a general rule" , "Model - instance" .)