He talks excessively about fight, following milliner (10)
I believe the answer is:
chatterbox
'he talks' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'excessively about fight following milliner' is the wordplay.
'excessively about' becomes 'c' (abbreviation for circa. I am not sure about the 'excessively' bit.).
'fight' becomes 'box' (boxing is a kind of fighting).
'following' says to put letters next to each other.
'milliner' becomes 'hatter' (synonyms).
'box' put after 'hatter' is 'hatterbox'.
'c'+'hatterbox'='CHATTERBOX'
Can you help me to learn more?
(Other definitions for chatterbox that I've seen before include "one who talks a lot" , "Windbag" , "There's much talk from me" , "Gossip" , "One using plenty of gas" .)