Found American leaving Greek island (5)
I believe the answer is:
crete
'greek island' is the definition.
(I've seen this before)
'found american leaving' is the wordplay.
'found' becomes 'create' (to found is to establish or create).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'leaving' indicates named letters should be taken away.
'create' with 'a' taken out is 'CRETE'.
(Other definitions for crete that I've seen before include "Greek island, site of the Minoan civilisation" , "Mediterranean island with Minoan remains" , "Greek island, capital Heraklion" , "Large Greek island" , "Erect (anag) - Mediterranean island" .)