Poet briefly working as comedian (6)
I believe the answer is:
keaton
'comedian' is the definition.
(silent comedy actor Buster Keaton)
'poet briefly working' is the wordplay.
'poet' becomes 'Keats' (John Keats).
'briefly' means to remove the last letter.
'working' becomes 'on' (on can mean working or activated).
'keats' with its final letter taken off is 'keat'.
'keat'+'on'='KEATON'
'as' acts as a link.
(Other definitions for keaton that I've seen before include "Buster - - , US comic" , "Buster ...... was poker-faced star of silent screen" , "Buster -, US film comedian" , "Buster . . . . . ., early film comedian" , "Buster -, US film actor" .)