Mad character to talk having lost head (6)
I believe the answer is:
hatter
'mad character' is the definition.
(Alice In Wonderland)
'talk having lost head' is the wordplay.
'talk' becomes 'chatter' (chattering is a kind of talking).
'having lost head' means to remove the first letter.
'chatter' with its initial letter taken off is 'HATTER'.
'to' is the link.
(Other definitions for hatter that I've seen before include "Tea-party holder" , "Milliner" , "Tea-party attender" , "Topping chap" , "There's a Mad one in 'Alice in Wonderland'" .)