Creative spark (4)
'creative spark' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for idea that I've seen before include "Purpose" , "a wheeze" , "Mental impression" , "Thought; concept" , "Proposal" .)
(Other definitions for inspiration that I've seen before include "Breathtaking" , "Sudden brilliant idea" , "Arousal to creativity" , "Creative thought" , "bright idea?" .)