Fruit is in water (6)
I believe the answer is:
raisin
'fruit' is the definition.
(raisin is a kind of fruit)
'is in water' is the wordplay.
'in' is an insertion indicator.
'water' becomes 'rain' (rain is a kind of water).
'is' placed inside 'rain' is 'RAISIN'.
(Other definitions for raisin that I've seen before include "fruit product" , "Dried red grape" , "Dried fruit" , "A dried grape, nice in cake" , "Dried 18" .)