It has water all round and has a tenant (5)
I believe the answer is:
islet
'it has water all round and has a tenant' is the definition.
The definition suggests a singular noun which matches the answer.
'it has water all round' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'has' is a charade indicator (letters next to each other).
'water' becomes 'elsi' (I can't justify this - if you can you should give a lot more credence to this answer).
'all round' shows that the letters should be reversed in order (all the words are reversed).
'elsi' written backwards gives 'isle'.
't' put after 'isle' is 'ISLET'.
Can you help me to learn more?
(Other definitions for islet that I've seen before include "small key?" , "Tiles to make a small island" , "Tiles (anag.)" , "Very small area surrounded by water" , "Stile (anag)" .)