Hugo or Charlie’s eccentric comic brother (7)
I believe the answer is:
groucho
'comic brother' is the definition.
(I know this)
'hugo or charlie's eccentric' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet).
'eccentric' indicates anagramming the letters.
'hugo'+'or'+'c'='hugoorc'
'hugoorc' with letters rearranged gives 'GROUCHO'.
(Other definitions for groucho that I've seen before include "One of Harpo's brothers" , "A Marx; a club" , "Funny man" , "The Marx Brother with the moustache" , "One of Marx Brothers" .)