Mean to be wasting years? Not altogether (6)
I believe the answer is:
stingy
'mean' is the definition.
(both can mean miserly)
'to be wasting years? not altogether' is the wordplay.
'not altogether' indicates a hidden word (some but not all of the letters in the clue).
'STINGY' is hidden in the letters of 'to wasting years'.
(Other definitions for stingy that I've seen before include "Small" , "Mean, niggardly" , "Tight-fisted, like 25 and 22 Across" , "like a bee" , "Patch of nettles is" .)