Adds fuel to (6)
I believe the answer is:
stokes
'adds fuel to' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stokes that I've seen before include "Builds up a fire" , "Feeds (a furnace)" , "Viscosity units; fuels (furnace)" , "Adds coal to (a furnace)" , "Shovels coal into furnace" .)