Look over island on river (5)
I believe the answer is:
loire
'river' is the definition.
(Loire is an example)
'look over island on' is the wordplay.
'look' becomes 'lo'.
'over' is a charade indicator (letters next to each other).
'island' becomes 'i'.
'on' becomes 're' ('on' can be mean 'with reference to'**).
'lo'+'i'+'re'='LOIRE'
(Other definitions for loire that I've seen before include "banker" , "department in France" , "Current French" , "France's longest river" , "French department" .)