Small body of water, and reducing in size? (4,3)
I believe the answer is:
aral sea
'small body' is the definition.
The definition suggests a singular noun which matches the answer.
'water and reducing in size?' is the wordplay.
'water' becomes 'sea' (the sea is water).
'and' means one lot of letters go next to another.
'reducing in size?' becomes 'aral' (I am not sure about this - if you are sure you should believe this answer much more).
'sea' after 'aral' is 'ARAL SEA'.
'of' is the link.
Can you help me to learn more?
(Other definitions for aral sea that I've seen before include "Saltwater lake" , "Shrunken lake" , "Large lake now largely desert" .)