Water goddess? (4)
I believe the answer is:
isis
I believe this clue is a double definition.
'water' is the first definition.
(I've seen this before)
'goddess?' is the second definition.
(Egyptian god)
(Other definitions for isis that I've seen before include "banker in Oxford" , "Revered figure" , "Oxfordshire river" , "Egyptian deity" , "A dark blue flower" .)