Concepts, notions (5)
I believe the answer is:
ideas
This clue is a double definition.
'concepts' is the first definition.
(I've seen this before)
'notions' is the second definition.
(I've seen this in another clue)
(Other definitions for ideas that I've seen before include "Notions, concepts" , "Brain waves" , "plans" , "Thoughts, personal views" , "Theories" .)