The 'silent' Marx brother (5)
I believe the answer is:
harpo
'the silent marx brother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for harpo that I've seen before include "Silent Marx brother" , "one from family of comedians" , "One of the Marx Brothers" , "brother who never speaks" , "speechless brother" .)