Are you in Cannes with stars where bankers end up? (9)
I believe the answer is:
estuaries
'where bankers end up?' is the definition.
(where rivers go - rivers are things that bank)
'are you in cannes with stars' is the wordplay.
'are you in cannes' becomes 'es tu' ('are you' in French, eg in Cannes).
'with' is a charade indicator (letters next to each other).
'stars' becomes 'aries' (constellation).
'estu'+'aries'='ESTUARIES'
(Other definitions for estuaries that I've seen before include "Broad mouths of rivers" , "coastal features" , "Tidal river mouths" .)