Superfluous (6)
I believe the answer is:
otiose
'superfluous' is the definition.
(I know that superfluous can be written as otiose)
This is the entire clue.
(Other definitions for otiose that I've seen before include "Indolent, ineffectual" , "Laze, idle" , "Without practical purpose" , "Idle, empty" , "Slothful" .)