Father keeps me in new hats (6)
I believe the answer is:
thames
'father' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?
'me in new hats' is the wordplay.
'in' is an insertion indicator.
'new' indicates an anagram.
'hats' anagrammed gives 'thas'.
'me' going into 'thas' is 'THAMES'.
'keeps' is the link.
Can you help me to learn more?
(Other definitions for thames that I've seen before include "It flows through London" , "The Ma's in the river" , "London flood control" , "One going to live abroad" , "London's river (6)" .)