Cookout residue (3)
I believe the answer is:
ash
'cookout residue' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ash that I've seen before include "Variety of tree" , "Wooden" , "Tree with winged seeds" , "One [TYPE OF TREE]" , "Remains from the yule-log?" .)