Concept or idea (7)
I believe the answer is:
thought
I believe this clue is a double definition.
'concept' is the first definition.
(I have seen 'A concept' mean 'thought' so perhaps 'concept' could also mean 'thought')
'idea' is the second definition.
(I know that idea can be written as thought)
(Other definitions for thought that I've seen before include "Musing" , "just a trifle" , "Deliberation" , "Idea, concept" , "Idea coming to mind" .)