Without idling, not starting (7)
I believe the answer is:
lacking
'without' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for lacking that I've seen before include "Being without, wanting" , "Missing" , "Short" , "Absent, deficient" , "Deficient or inadequate" .)