Thought "I won't get into trouble" (6)
I believe the answer is:
notion
'thought' is the definition.
(notion is a kind of thought)
'i won't get into trouble' is the wordplay.
'i won't' becomes 'no' (refusal).
'get' is an insertion indicator.
'trouble' indicates an anagram.
'into' with letters rearranged gives 'tion'.
'no' put within 'tion' is 'NOTION'.
(Other definitions for notion that I've seen before include "clue" , "Idea or fancy" , "Vague or fanciful idea" , "Vague impression" , "Concept, belief" .)