Rubbish set alight by crowd (8)
I believe the answer is:
landfill
'rubbish set' is the definition.
(a set or amount of rubbish)
'alight by crowd' is the wordplay.
'alight' becomes 'land' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'crowd' becomes 'fill' (as in filling or crowding into a space).
'land'+'fill'='LANDFILL'
(Other definitions for landfill that I've seen before include "Rubbish buried in site" , "Buried waste material" , "Disposal of waste by burial" , "Disposal of waste by burying" , "Rubbish disposal site" .)