Design it? I only should cover lighting (8)
I believe the answer is:
ignition
'lighting' is the definition.
(synonyms)
'design it? i only should cover' is the wordplay.
'cover' says the answer is hidden in the clue (I've seen 'covered' mean this (the answer is covered up by the clue)).
'IGNITION' is hidden in the letters of 'design it i only should'.
(Other definitions for ignition that I've seen before include "Act of starting a fire" , "Car engine starter" , "Beginning of combustion" , "Process of starting fire" , "Mechanism to start car engine by sparking fuel" .)