Model of lamp thrown into river (7)
I believe the answer is:
example
'model' is the definition.
('example' can be a synonym of 'model')
'lamp thrown into river' is the wordplay.
'thrown' is an anagram indicator.
'into' means one lot of letters goes inside another.
'river' becomes 'exe' (I've seen this before).
'lamp' is an anagram of 'ampl'.
'ampl' going into 'exe' is 'EXAMPLE'.
'of' is the link.
(Other definitions for example that I've seen before include "Specimen, illustration" , "Something to be imitated" , "Thing illustrating a general rule" , "Instance or illustration" , "lesson" .)