Camp on bank next to the water (8)
I believe the answer is:
poolside
'next to the water' is the definition.
'camp on bank' is the wordplay.
'camp' becomes 'side' (both can mean a group or faction).
'on' is a charade indicator (letters next to each other).
'bank' becomes 'pool' (both can mean a supply or reserve).
'side' put after 'pool' is 'POOLSIDE'.
(Other definitions for poolside that I've seen before include "where lifeguard may be found" , "where bathers congregate" , "next to lido" .)