Aching to seize half of rabble's fuel (8)
I believe the answer is:
paraffin
'fuel' is the definition.
(I know that paraffin is a type of coal oil)
'aching to seize half of rabble's' is the wordplay.
'aching' becomes 'pain' (aching is pain or hurt).
'to seize' indicates putting letters inside.
'half of' suggests halving the letters.
'rabble' becomes 'riffraff' (both can mean ordinary people).
'riffraff' cut in half is 'raff'.
'pain' going around 'raff' is 'PARAFFIN'.
(Other definitions for paraffin that I've seen before include "Liquid fuel" , "Waxy flammable substance" , "Kerosene" , "Fuel oil obtained from petroleum or coal" , "Flammable wax" .)