Disease could be spread by water (7)
I believe the answer is:
seaside
'spread by water' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'disease could be' is the wordplay.
'could be' is an anagram indicator.
'disease' with letters rearranged gives 'SEASIDE'.
Can you help me to learn more?
(Other definitions for seaside that I've seen before include "Holiday destination" , "Disease (anag) -- coast" , "Ocean shore" , "holiday venue" , "By the briny" .)