Game starts to slide, creating unruly crowd (8)
I believe the answer is:
scrabble
'game' is the definition.
(Scrabble is a board game)
'starts to slide creating unruly crowd' is the wordplay.
'starts to' suggests taking the first letters.
'unruly crowd' becomes 'rabble' (rabble can mean a crowd or mob).
The first letters of 'slide creating' is 'sc'.
'sc'+'rabble'='SCRABBLE'
(Other definitions for scrabble that I've seen before include "Root around" , "Scratch for popular word game" , "Very popular word-board gane" , "Board game with letters" , "Popular word game using board" .)