Waste of time, what you may do to protect the environment? (7)
I believe the answer is:
useless
'waste of time' is the definition.
(something useless is a waste of time)
I can't explain the rest of the clue.
(Other definitions for useless that I've seen before include "Lacking in purpose" , "Fruitless" , "Poor" , "Without any worthwhile application" , "Unserviceable" .)