I can dispense with the candle: it's useless (4)
I believe the answer is:
idle
'useless' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for idle that I've seen before include "Frivolous" , "Monty Python team member" , "lndolent" , "out of a job" , "Explosive stuff" .)