Prisoner's robbery scheme (10)
I believe the answer is:
conspiracy
'scheme' is the definition.
(I know that conspiracy is a type of game)
'prisoner's robbery' is the wordplay.
'prisoner's' becomes 'con's' (abbreviation for 'convict').
'robbery' becomes 'piracy' (piracy is a kind of robbery).
'cons'+'piracy'='CONSPIRACY'
(Other definitions for conspiracy that I've seen before include "Secret plan" , "scheme" , "Joint action undertaken secretly" , "that involves plotting" , "Plot" .)