Sega ultimately crashed, playing game (8)
I believe the answer is:
charades
'game' is the definition.
(I know that charades is a type of guessing game)
'sega ultimately crashed playing' is the wordplay.
'ultimately' says to take the final letters.
'playing' is an anagram indicator.
The final letter of 'sega' is 'a'.
'a'+'crashed'='acrashed'
'acrashed' is an anagram of 'CHARADES'.
(Other definitions for charades that I've seen before include "Games like this" , "Game in which answers are acted out" , "Miming games" , "Miming parlour game" , "Party guessing game" .)