Tank on banks of Seine river to see in Paris (9)
I believe the answer is:
reservoir
'tank' is the definition.
(I know that reservoir is a type of tank)
'on banks of seine river to see in paris' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'banks of' suggests removing the centre (the banks are the sides of the word).
'river' becomes 'r' (abbreviation).
'to see in paris' becomes 'voir' (to see in French).
'seine' with its middle removed is 'se'.
're'+'se'+'r'+'voir'='RESERVOIR'
(Other definitions for reservoir that I've seen before include "Lake used to store water for community use" , "Artificial lake" , "Area for storage, of water say" , "Man-made lake or tank" , "Man-made lake of stored water" .)