What’s in wet areas, affected by storms? (8)
'what's in' is the definition.
I can't judge whether this defines the answer.
'wet areas affected by storms?' is the wordplay.
'affected by storms?' is an anagram indicator (the order of letters in a stormy condition).
'wetareas' is an anagram of 'SEAWATER'.
(Other definitions for seawater that I've seen before include "Drink", "Brine", "What breaches dyke, perhaps".)