Combustible heap (4)
I believe the answer is:
pyre
'combustible heap' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for pyre that I've seen before include "centrepiece of funerary rite" , "Heap of wood for ritually burning a body" , "Funeral mound" , "Part of Eastern death rite" , "Heap of combustible material for burning a body" .)