Part of Robin Goodfellow’s game (5)
I believe the answer is:
bingo
'game' is the definition.
(bingo is a game)
'part of robin goodfellow's' is the wordplay.
'part of' says the answer is hidden in the clue.
'BINGO' is hidden in the letters of 'robin goodfellows'.
(Other definitions for bingo that I've seen before include "Lotto" , "Housey-housey" , "Number game" , "Game of chance" , "Cry on discovering something" .)