A bird so loveless and sickly (4)
I believe the answer is:
swan
'a bird' is the definition.
(I know that swan is a type of aquatic bird)
'loveless and sickly' is the wordplay.
'loveless' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'and' means one lot of letters go next to another.
'sickly' becomes 'wan' (I've seen this before).
's'+'wan'='SWAN'
'so' acts as a link.
Can you help me to learn more?
(Other definitions for swan that I've seen before include "Large waterbird" , "possibly mute" , "black, in 7th" , "Large water bird" , "Cob - pen" .)