Pointless, vain (6)
I believe the answer is:
futile
This clue is a double definition.
'pointless' is the first definition.
(I've seen this before)
'vain' is the second definition.
(I know that vain can be written as futile)
(Other definitions for futile that I've seen before include "Fruitless" , "If lute is altered it becomes ineffectual." , "Useless or vain" , "Pointless, a waste of effort" , "Ineffectual, a waste of time" .)