He has shares in a houseboat, but no fixed address (4)
I believe the answer is:
hobo
'he has shares in a houseboat but no fixed address' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he has shares in a houseboat' is the wordplay.
'he' becomes 'Bo'.
'has' says to put letters next to each other.
'shares in a houseboat' becomes 'ho' (I can't justify this - if you can you should give a lot more credence to this answer).
'bo' after 'ho' is 'HOBO'.
Can you help me to learn more?
(Other definitions for hobo that I've seen before include "Homeless American" , "Tramp (US)" , "Vagrant (American)" , "Vagrant, tramp" , "Bum" .)