Fellow of trite demeanour (3)
I believe the answer is:
ted
'fellow' is the definition.
(man's name)
'of trite demeanour' is the wordplay.
'of' indicates a hidden word.
'TED' is hidden within 'trite demeanour'.
(Other definitions for ted that I've seen before include "Edward, in short" , "Hang out to dry" , "Turn over (hay); man's name" , "Familiar form of Edward" , "Father ..., Dermot Morgan's TV creation" .)