There's much talk from me about supposedly mad character on strike (10)
I believe the answer is:
chatterbox
'there's much talk from me' is the definition.
(I've seen this before)
'about supposedly mad character on strike' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa'**).
'supposedly mad character' becomes 'hatter' (the Mad Hatter from Alice in Wonderland).
'on' says to put letters next to each other.
'strike' becomes 'box'.
'c'+'hatter'+'box'='CHATTERBOX'
(Other definitions for chatterbox that I've seen before include "Talkative person" , "one who talks a lot" , "Gasbag" , "Babbler" , "Gossip" .)