Nasty disease spread by water (7)
I believe the answer is:
seaside
'spread by water' is the definition.
The definition and answer can be both natural objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'nasty disease' is the wordplay.
'nasty' 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 "Ocean shore" , "Shore - disease (anag)" , "Popular resort area" , "Shoreline" , "holiday location" .)