Former lover with big bosom, essentially models (8)
I believe the answer is:
examples
'models' is the definition.
('example' can be a synonym of 'model')
'former lover with big bosom essentially' is the wordplay.
'former lover' becomes 'ex'.
'with' is a charade indicator (letters next to each other).
'big' becomes 'ample' ('ample' can be similar in meaning to 'big'**).
'essentially' means to look at the middle letters.
The central letter of 'bosom' is 's'.
'ex'+'ample'+'s'='EXAMPLES'
(Other definitions for examples that I've seen before include "Expels ma for pieces of conduct worthy of imitation" , "Illustrations, instances" , "Specimens" , "Things characteristic of their kind" , "prototypes" .)