Hasbro's "game of unspeakable fun" (5)
I believe the answer is:
taboo
'hasbro's game of unspeakable fun' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for taboo that I've seen before include "Beyond the pale" , "Not permitted" , "Socially forbidden" , "Prohibited by religion or custom" , "Forbidden for social reasons" .)