Complete madman losing head (5)
I believe the answer is:
utter
'complete' is the definition.
(I know that complete can be written as utter)
'madman losing head' is the wordplay.
'madman' becomes 'nutter' (I've seen this before).
'losing head' means to remove the first letter.
'nutter' with its initial letter taken away is 'UTTER'.
(Other definitions for utter that I've seen before include "State - unqualified - rank" , "Express audibly" , "mouth" , "Without a single qualification" , "Speak; complete" .)