That plucky Marx Brother? (5)

I believe the answer is:

harpo

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'marx brother?' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for harpo that I've seen before include "Silent Marx brother" , "The dumb Marx brother" , "The mute Marx Brother" , "one from family of comedians" , "silent film star" .)

I've seen this clue in the Evening Standard.

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